Blender Git Loki

Restored Fluid Sim baking

This commit restores fluid sim baking functionality in 2.5, it's been on the todo for
a while, and was previously almost completely non-functional. The old
code was quite complicated and specific to the 2.4 animation system, so I've
pretty much rewritten most of it.

This includes:
* Animated variables work again - just key them in the UI. Non-animateable values
should be already set non-animateable in RNA, hopefully I got them all.

Available are: Domain Gravity / Domain Viscosity / Object loc/rot/scale /
Object initial velocity / Deforming meshes / Fluid control Attract strength /
Fluid control Attract radius / Fluid control Velocity strength /
Fluid control Velocity radius / Object Active status (checkbox next to fluid type)

The Domain time scale is still not yet implemented.

* Fluid sim now use global scene units data by default - when enabled, the
scene's global gravity value is used and when units are set (metric/imperial)
the simulation real world size is taken from the object's actual measurements.

* The baking process is now done in the background, using the nifty threaded
Jobs system. It's non-blocking and your domain object will show the simulated
fluid as it becomes available for that frame.

A nice extra thing for the future would be to improve the visualisation of the
object's state while baking, and also the jobs system/ui could do with some
touchups - currently it has to share a bit from the 'render' job, and appears as
'Render' in the header. Progress bars for jobs in the header would be great too.