The Python API to define Panels and Operators is based on subclassing,
this makes that system more generic, and based on RNA. Hopefully that
will make it easy to make various parts of Blender more extensible.
* The system simply uses RNA properties and functions and marks them
with REGISTER to make them part of the type registration process.
Additionally, the struct must provide a register/unregister callback
to create/free the PanelType or similar.
* From the python side there were some small changes, mainly that
registration now goes trough bpy.types.register instead of
bpy.ui.addPanel.
* Only Panels have been wrapped this way now. Check rna_ui.c to see
how this code works. There's still some rough edges and possibilities
to make it cleaner, though it works without any manual python code.
* Started some docs here:
http://wiki.blender.org/index.php/BlenderDev/Blender2.5/RNATypeRegistration
* Also changed some RNA_property and RNA_struct functions to not
require a PointerRNA anymore, where they were not required (which
is actually the cause of most changed files).
* Widgets now get coloured when driven. The colour used is debatable, but I've just set it to a purplish colour so that it's easy to distinguish from animated/keyframes/highlight colours.
* New drivers are given generator F-Curve modifiers by default so that they at least show up in the view.
Drivers can now be Added/Removed from buttons using the D/Alt-D hotkeys, and also through the menu. Driver settings (i.e. the target) are not set by default. To set those, go to the Graph Editor (see notes).
Notes:
* Buildsystem maintainers - I've added a new file "editors/animation/drivers.c"
* Widget colours for the driven-setting indications are needed
* To see the new drivers, go into Graph Editor -> "Drivers" mode. Currently, there's a little bug there which prevents editing of the new drivers.
