Blender Git Loki

Make caching a bit more sane (fixes plasticity issue)

This cleans up the cloth caching logic a bit.

Now, a simulation step only occurs if the current time is exactly one
frame after the last simulated step, thus preventing time gaps and
runtime data corruption. Also, now the cloth is only re-initialized
if the cache is actually outdated, instead of always being reset when
on the first frame.

This solves a bug where the cache was freed when moving the time to
a point within the cached period.

These changes also fix the issue of non-cached runtime simulation state
properties (e.g. plasticity) being reset when going to the first frame
or retaining a future state when simulating over an existing cache with
time gaps.