Caelum Code

Remove one unused function declaration.

Set CaelumDemo exe name to CaelumDemo.exe (instead of caelumtest1)

Restore precompiled header use in release mode with visual studio.

Cleanup vcproj files and make it almost build with 1.7 (CaelumLab can't be made to link out of the box with both 1.6 and 1.7).
Slightly cleanup PostBuild.bat: Always use windows slash order; fail if OGRE_HOME is mising; improve path echo message.

Revert CaelumPrerequisites to properly compile against the official ogre 1.6.2 release.

Implemented linear slope bias for sample materials based on alpha rejection

Fix compilation with versions later than 1.6.2 related to streaming Ogre::Degree

Added script variables for all materials used in samples. Make transparent objects cast shadow correctly.

Drop shadow_caster_material in script and always propagate alpha in a single default shadow caster.

Initial shadow support for alpha rejection in sample shader