Main Feature:
* It is now possible to choose which AnimData block is the 'active' one for editing, and/or select them too. AnimData blocks are generally the dark blue and lighter-blue expanders (i.e. Scene, Object, Camera, Lamp, Curve, Armature, etc.)
* Objects are no longer selected/deselected when AKEY is used to toggle selection of channels. This was getting a bit annoying.
* Following on from selection of AnimData blocks, it is now possible to select/make active an AnimData block in the animation editors, and change the active action for that block via the 'Animation Data' panel in NLA Editor's properties region.
--> Be aware that user-counts are not totally handled correctly there yet, so some funky behaviour might be seen...
--> It is possible to assign a new action, or to assign an existing one, allowing to switch between actions as in the past with Actions/IPO Editors...
Other tweaks:
* Some code tweaks towards making the 'Euler Filter' feature for Graph Editor working sometime soon
* Added some backend code for snapping the values of keyframes to a single value. Still need to work out some UI for it though.
* Shuffled the code for ACT_OT_new() around, and removed the poll() callback so that it worked in NLA too.
* Fixed some more notifier bugs with deleting bones and a few other editmode operations for Armatures.
* F-Modifier API is now in its own file in blenkernel
* Renamed and refactored these so that they're no dependent on F-Curves, since all they really used was the fcu->modifiers list
* Added missing license blocks to a few files
For now, some of these polls may be a bit too restrictive, but at least we have some unified+cleaned bases to work from now (instead of relying on the generic ED_operator_area_active).
