Blender Git Loki

UI: allow fractical unit size for layouts.

UI: use pie menu for snap, pivot and proportional editing.

* Proportional pie menu at shift+O.
* Snap pie menu at shift+S.
* Pivot pie menu at comma. Previous comma, ctrl+comma, period
and ctrl+period shortcuts for specific pivot types were removed.

Ref T56881.

Depsgraph: Add missing relation for spline IK

Solver should clearly depend on initializaiton.

Cloth: Collision improvements

This commit includes several performance, stability, and reliability
improvements to cloth collisions.

Most notably:
* The implementation of a new self-collisions system.
* Multithreading of collision detection.
* Implementation of single sided collisions and normal overrides.
* Replacement of the `plNearestPoints` function from Bullet with a
dedicated solution.

Further, this also includes several bug fixes, and algorithmic
improvements.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D3712

Addons: reactivate 'STL format' addon

Reviewers: brecht

Differential Revision: https://developer.blender.org/D3735

Cleanup: Edit Surface & Curve engines unused code

Edit Surface: Use edit curve engine to display edit surface

It's so similar in practice that we don't need a separate engine for edit
surface overlays.

Edit Curve: Fix "show handles" option hiding nurbs segments

GP: Only check annotation origin for 3D View

GP: Rename parameter unlock_color and tooltip

GP: Fix unreported crash when click+drag in edit mode

GP: Change menu icons for hide/show

Implement additional modes for Shrinkwrap to a surface.

In addition to the original map to surface and Keep Above Surface,
add modes that only affect vertices that are inside or outside
the object. This is inspired by the Limit Distance constraint,
and can be useful for crude collision detection in rigs.

The inside/outside test works based on face normals and may not be
completely reliable near 90 degree or sharper angles in the target.

Reviewers: campbellbarton, mont29

Differential Revision: https://developer.blender.org/D3717

GP: Fix unreported change material operator error

The first material of the list could not be assigned.

Fix T56926: Highlighted selection doesn't disappear when locking layer

Multires: Use proper subdivision level for reshape

Apparently, part of code got lost last minute prior to push.

Fix T56899: mesh deform bind does not work.

Multires: Promote OSD CCG to be officially supported

Only active when WITH_OPENSUBDIV_MODIFIER is set to ON.

There is still some work to be done to make that one enabled by
default.

Subsurf: Tweak versioning code

Select minimum of render subdivision levels and 3 for
the initial value of quality. This way we don't force
too much quality for meshes which were not supposed to
be too much quality :)

Fix crash opening some old files, after recent changes.