Added configurable Z bias to Text3D effect.
Default Text effect color changed to opaque black.


git-svn-id: http://urho3d.googlecode.com/svn/trunk@2658 3bd170d8-ddcf-f82c-f583-7a401ccf5608
Fix enum.

git-svn-id: http://urho3d.googlecode.com/svn/trunk@2659 3bd170d8-ddcf-f82c-f583-7a401ccf5608