Blender Git Loki

Fix/properly implement: "make group proxy"

This was never correctly implemented. It now works as expected (ala 2.79 behaviour).
The proxy object is added to all the collections of the original empty.

Before not only this wasn't the case, but it would crash Blender.

Merge branch 'master' into blender2.8

Correct last commit, use WM_exit

Without this temp directory isn't removed.

Exit with invalid command line arguments

Loading blender with an unknown name would interpret it as a blend file.

This meant passing `--arg` arguments would end up creating new
blend files which could be confusing if you made a typo on a command
line argument.

Now check the string has a blend file extension,
exiting if it doesn't.

Merge branch 'master' into blender2.8

Depsgraph: Use new ID copy API to copy scenes

Avoids temporary main and datablock memory from being allocated.

Allow non-initialized memory to be passed to BKE_id_copy_ex

This only applies when LIB_ID_CREATE_NO_ALLOCATE flag is used and guarantees
that non-memset-zero memory can be used (or, that same memory chunk might be
used over and over again without need to clean it from the calleer).

Fix operators adding manipulators multiple times

Running spin or bisect twice in a row added widget groups each time.

Add note about handling of root nodetree in ID copydata.

OUr beloved root nodetrees... Had to check again the code to undersand
why we copy them with bmain even though they are not in bmain, so this
is worth a comment. ;)

Cycles: Add extra logging in CUDA device detection code

Merge branch 'master' into blender2.8

Merge branch 'master' into blender2.8

Merge branch 'master' into blender2.8

Merge branch 'master' into blender2.8

Merge branch 'master' into blender2.8

Cleanup: redundant comments

Class names are readable, no need for explanations of each one.

UI: 3D View, object menu

Changes from D2876 by @meta-androcto /w own edits

- Move "Relations" into own menu.

UI: 3D View, undo menu reorganization

Changes from D2876 by @meta-androcto /w own edits

Move 3x undo items into Undo menu,
these are such common operations they're typically accessed by keys.

Also add to menus which didn't have undo
(seemed random which modes had undo, undo history in their menus).

UI: 3D View, minor menu reorganization

Changes from D2876 by @meta-androcto

- Move "Delete" to the first menu item in most toplevel menus.
- Add separators.
- Consistent order of Undo/Redo

UI: 3D View Mesh "Select" menu reorganization

Changes from D2876 by @meta-androcto /w own edits

- Move "Select Linked" into own menu.
- Move "Select Loop" into own menu.