Blender Git Loki

Animation: allow specifying a custom frame range for actions.

Some operations, e.g. adding a new action strip to NLA, require
knowing the active frame range of an action, but currently it can
only be deduced by scanning the keyframes of the curves within it.
This is not ideal if e.g. curves are staggered for overlap.

As suggested by Nathan Vegdahl, this patch adds Action properties
that allow manually specifying its active frame range, and whether
it is intended to be cyclic. The settings are exposed in a popover
in Action Editor. When enabled, the range is highlighted in the
background using a striped fill to distinguish it from the solid
filled regular playback range.

When set, the frame range is used by NLA. In addition, the Cycle-Aware
Keying option automatically sets up F-Curves newly added to a cyclic
action to use cyclic extrapolation with the correct period.