Change design of Geometry properties UI panel:
    - now, you only can apply one type of special geometry at time.
    - before, if you activate 'portal light' and 'volume object', at the same object
      only one of this propertiess are applied.
Change design of Geometry properties UI panel:
    - now, you only can apply one type of special geometry at time.
    - before, if you activate 'portal light' and 'volume object', at the same object
      only one of this propertiess are applied.
Create 'Object.bounty' subclass derivated of Object.
Refine StrandParticles code and allow the use of 'Clay' metrial.
Add small comments and Style code changes.