removal of MOAIProp:setParent and add of BlendModes

- displayObj prop isnow aliased by renderTable to 'simplify'
displayObjContainer logic and to extend possibility to define logical
simple displayObj made by multiple moaiprop object
- setParent has been replaced by setAttrLink / clearAttrLink, also with
specific logic for geometrical transformation and colors
- added BlendMode logic with removal of 'default'
- more investigation needed about textfield blendmode logic