Material properties are accumulative along the node tree
Handle NiVertexColorProperty
Handle NiZBufferProperty
Handle NiSpecularProperty
Add missing depthFlags to the hash
Fix/workaround specular issues

The glossiness should not be multiplied by 255, however the values set in many
of Bloodmoon's meshes would look horrible otherwise. Now we can let the
NiSpecularProperty specify when to enable specular (which is supposed to
default to on, but due to the aforementioned meshes, we default to off).
Convert some BooleanValues to StringValues
Merge remote-tracking branch 'zini/master' into material-fix

Conflicts:
	components/nifogre/ogrenifloader.cpp