2.5 Python

2.5 Python

Merging changes made by Arystanbek in the soc-2009-kazanbas branch,
plus some things modified and added by me.

* Operator exec is called execute in python now, due to conflicts
  with python exec keyword.
* Operator invoke/execute now get context argument.
* Fix crash executing operators due to bpy_import_main_set not being
  set with Main pointer.
* The bpy.props module now has the FloatProperty/IntProperty/
  StringProperty/BoolProperty functions to define RNA properties for
  operators.
* Operators now have an __operator__ property to get the actual RNA
  operator pointers, this is only temporary though.
* bpy.ops.add now allows the operator to be already registered, it
  will simply overwrite the existing one.
* Both the ui and io directories are now scanned and run on startup.