Add normal mapping option to Shader technique

Replaces the ShaderNormalMapped technique.
Fix wrong texture address mode for normal map
Remove now obsolete ShaderNormalMapped technique.
Use default normal texture if none is available.

For terrain layers when using normal mapping.
Add terrain material recompiled signal.
Reload terrain pages on preferred technique change
Improve reload speed on terrain technique change
Use Ogre LOD for normal mapped terrain as well.

When normal mapping is enabled, creates two techniques in the terrain
material. Normal mapping is only used for objects which are closer than
50 units. Otherwise, normal shaded terrain is used.
Disable terrain debug text in performance widget

Produced Lua errors and is not particularly useful with the Ogre Terrain
Component.
Enable self-shadowing on terrain.

The correct shadow-caster-material needed to be set.