Ported the following tools
* borderselect
* invert selection
Note: while porting these, I noticed a few issues with some stuff that still needs to be cleaned up.
Events handling in scrollers won't work yet, for the useful select all in frame(-range) or select all in channel(s). We should probably review ways to expose this more clearly in the UI too.
* Re-exposed relevant parts of anim_keyframing.c code that doesn't have external dependencies.
* Added get_active_posechannel() to blenkernel api for poses/posechannels to solve the only missing link I found. This should have been moved there ages ago!
Moved time_ops.c contents to anim_ops.c, as the operators there are applicable to all other Animation Editors too. anim_ops.c will therefore contain all operators which will apply to all Animation Editors (i.e. change frame, frames/seconds display toggle, and soon Preview Range tools).
As such, added new global 'Animation' keymap like for View2D and Markers, which will ensure that these tools can be accessed in an uniform way across editors.
Note that the order that these things are added is important, as the Animation ones will often 'steal' events from the View2D and Markers ones if placed before the others. To prevent that, we'd need to be able to set boundboxes here...
