Added parsing external graphics and add new layer params (camera position and camera mouse enable)
Added assembling external graphics, refactoring. (Still need rework adding camera, but first need to do appropriate changes in engine)
Fixed comment
Implemented new layers and cameras organization
Reworked related to new layers and cameras organization
removed 'keepGroup' from layer
Now layers and cameras creates correctly
Support parsing and assembling  new properties 'repeatable' & 'keepSequence' of  graphics scheme
Clean code