* Added very basic loading of .py files on startup to define panels.
It now executes all .py files in .blender/ui on startup. Right now
this contains the object buttons, the C code for it is commented out.
These files should get embedded in the blender executable as well
eventually, that's a bit more complicated so this works for now.
* For scons and cmake it seems to copy & find the files OK, for make
only "make release" works (same with scripts/ folder it seems).
* Added BLI_gethome_folder function in BLI_util.h. This is adapted
from bpy_gethome, and gives the path to a folder in .blender like
scripts or ui.
There's plenty of things to figure out here about paths, embedding,
caching, user configs ...
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