Freestyle: Fix for UI text of the "use_tips" line style property.
Freestyle: added a note on #include "DNA_material_types.h".
Freestyle: removed the context switch button from the Freestyle panel in the Render properties window.

The button was intended to guide new users of Freestyle, but actually that is a matter
of documentation.  The button is unlikely to be frequently used once users get familiar
with Freestyle panels in other contexts.  Now that Freestyle has been part of Blender
since a while, it seems time to clean the UI.
Code cleanup, unneeded variable, always true when used, not used when
set
Tiny change for gsoc paint curve drawing: numpad enter now draws the curve too.
Update buildbot conf, to enable a 'testbuild' branch in 'force' scheduler.
Texture paint:

* paint slots from cycles only include texture image types
* tweaking with select mouse no longer confirms on release
Buildbot: fix submodule branch issue (we have to fix it on 'master', since default
one can be overriden by custom setting for force scheduler).
Fix crash in cases when first BA step happens with all zero-weighted tracks
Fix T41141, can't paint texture in cycles.

The issue is actually that creating a new image in texture paint mode
will set it always as a stencil image. Internally, the code checks if
the painted image is the same as the stencil and if it is, no painting
is done.

Solution is to expose a boolena to the operator for setting the image as
a stencil (could be an enum in th future for more uses)

Stencil UI is a bit weird here, will definitely redesign.
Freestyle: minor speedup by omitting unnecessary transform matrix operations in the file loader.

Previously the imported mesh data were transformed by a local-to-world projection matrix
through NodeTransform.  Now that the file loader assumes the imported mesh data already
in the camera coordinate system, an indentity matrix was supplied to NodeTransform.
The present commit avoids this redundant matrix operation by using NodeGroup instead of
NodeTransform, recalling the latter is a subclass of the former with extra matrix computations.
initial intersect code
initial isect
intersection script
test vert intersection
check for intersections where no new verts are added first
minor fixes
WIP
add vert-edge check
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