Blender Git Loki

Improvements of Freestyle GUI controls - Part 1.

This commit makes a set of fixes and improvements based on the results of
Freestyle branch review by Brecht. The discussion thread is:
http://lists.blender.org/pipermail/bf-committers/2012-October/037927.html

* The Layers panel and Freestyle-related panels in the Render tab of the
Properties window were moved to the newly created Render Layers tab.
The idea is to separate per render layer rendering options into a distinct
Properties window tab, and use the existing Render tab to accommodate
per scene rendering options.

* The new Freestyle panel was added in the Render tab. The panel header
contains a toggle button for globally enabling Freestyle, with the aim of making
Freestyle easier to find. Those Freestyle options in the Post Processing panel
were also moved to the new panel.

* GUI code was updated so that UI controls will be greyed out (instead of
being hidden) when Freestyle is disabled. Additional UI changes were also
made to reduce space consumption.

* The list of line sets was moved from the Freestyle panel to the Freestyle:
Line Sets panel.

* Old ray-casting algorithms were removed from the UI. Now only two
algorithms (culled and non-culled cumulative visibility detection algorithms)
are available, and the selection is done by the new "Culling" toggle button
within the edge detection options.