- added scenes / exScenes parameters to viewports, to
specify the only scenes to display / the scenes to exclude
from renderering in a given viewport : closes #7

- restructured/fixed some issues with "longTap"/"longStaticTap" event
detection, and selection /unselection of meshes : this solved the first
sub issue in #6
 * experimenting with orbit controls etc, to find a cleaner solution
to the pointer interactions issues etc