Blender Git Loki

This commit frees list ui items from their dependencies to Panel, and hence from all the limitations this implied (mostly, the "only one list per panel" one).

It introduces a new (py-extendable and registrable) RNA type, UIList (roughly similar to Panel one), which currently contains only "standard" list's scroll pos and size (but may be expended to include e.g. some filtering data, etc.). This now makes lists completely independent from Panels!

This UIList has a draw_item callback which allows to customize items' drawing from python, that all addons can now use. Incidentally, this also greatly simplifies the C code of this widget, as we do not code any "special case" here anymore!

To make all this work, other changes were also necessary:

* Now all buttons (uiBut struct) have a 'custom_data' void pointer, used currently to store the uiList struct associated with a given uiLayoutListBox.

* DynamicPaintSurface now exposes a new bool, use_color_preview (readonly), saying whether that surface has some 3D view preview data or not.

* UILayout class has now four new (static) functions, to get the actual icon of any RNA object (important e.g. with materials or textures), and to get an enum item's UI name, description and icon.

* UILayout's label() func now takes an optional 'icon_value' integer parameter, which if not zero will override the 'icon' one (mandatory to use "custom" icons as generated for material/texture/... previews).
Note: not sure whether we should add that one to all UILayout's prop funcs?

Note: will update addons using template list asap.

code cleanup:
- free_dverts -> BKE_defvert_array_free
- copy_dverts -> BKE_defvert_array_copy

also move the functions from BKE_mesh into BKE_deform

fix for memory leak with weight painting and ensure vertex group is created before use.

Add 'vertex_only' option to bevel tool.
Right now, changing segments to > 1 doesn't do anything,
but intend to work on making that cause rounded corners.

remove unneeded inline lookups and fix error with wpaint_stroke_test_start returning OPERATOR_PASS_THROUGH rather then a boolean.

remove workaround for [#31555], forcing PYTHONIOENCODING was causing stdout to be lost on exit - no MEM_printmemlist_stats()

Better error report when no camera is found.

While trying to render a RenderLayer from a linked scene, I couldnt tell why it wasnt doing anything. It just stopped rendering. Until I look on the console and see the No Camera print.

This commit replaces the simple terminal printf with an actual error report, that shows in both terminal and to the user:
http://pasteall.org/pic/show.php?id=42499

I believe this commit is pretty harmless, and only adds functionality. But feel free to remove it.

Outliner fix:

New "Blender file" viewer now shows names of libraries better.

Function IMB_onehalf was not freeing memory.
(Used for icon mipmap)

Fix in previous commit: forgot to free data from file reading.

(Campbell: we want the memory prints back!!!)

Bug fix, own collection.

"Add Group" was excluding linked library objects.

New features!

- Packing .blend files

If you work a lot with dynamic linked .blend files ("Libraries"), it's always hard to
share your work with others (or for bug reports!).
This new option packs all used external .blend files, and - on save - combines it together
in one .blend file. You can save that file on any location.

Loading a packed .blend file then loads all library data usual - not editable.

Just use unpack to save out all linked .blend files. This will only save out the files
according the directory structure as was used on linking - relative to the current .blend.
It will create new directories, so be careful with unpacking when relative paths go up.

This feature also works fine for linked compressed .blend files.

It also works for many levels deep linked .blend hierarchies.

Access is hidden for now - I need to get some people to give it serious testing first.
You can find the options via spacebar search (try pack or unpack).

- Packed data and Undo

Now all packed data is excluded from the Undo buffer storage. Keeps undo memory smaller
and makes faster redo possible.

validate operator names on startup (debug mode only)

use keyword args for bmesh.update_edit_mesh(...)

add option to BLI_scanfill_calc() - BLI_SCANFILL_CALC_HOLES, gives some speedup for BMesh ngons which never have holes and ensures predictable triangle count (totvert - 2), which is needed for pre-calculating array size.

correction for poly_to_tri_count() when given zero poly count.

remove realloc's during BMEdit_RecalcTessellation(), instead use poly_to_tri_count() to calculate how many triangles are needed.

display the number of tri's in object mode status, often requested feature from users who model for realtime/game-engine output,
the total number of faces wasn't so useful and could be especially misleading with ngons.

Fix: edge uv stitch mode did not average final position of uvs in
midpoint, non-snapping mode.

Fix: rotation of uv islands during stitch did not take uv aspect ratio
of image into account, distorting the islands. Now properly scale the
components before rotating the island.