Unification of brush code

* rename sculpt_brush_texture_settings to brush_texture_settings
* Expose texture scale and offset in texture paint mode
* Introduce still inactive mapping mode for texture paint, tiled and
view aligned only. Projective paint uses only tiled, while 2d paint can
use both. Commit will come that will use both appropriately for both
modes, omitting fixed brush flag (which is tiled with another name)

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53843 954f8c5b-7b00-dc11-b283-0030488c597c