Blender Git Loki

Fixed bug [#25649] Image editor paint icon missing until enter weight
paint

A couple underlying issues:

* Paint icon was looking only at the object mode to determine what the
"current" mode is, but that gave problems when the object mode was
anything other than texpaint, but 2D image paint was turned on. Fix
was to also look at what space is being drawn, and only if it's in
the 3D view does it look at the ob mode.

* The brushes lists weren't getting filtered correctly in the same
case where 2D image paint was on but a different object mode is
enabled. Fixed by changing the brush rna poll to look at the paint
source, rather than the object mode.