Added alignments for RenderGroups
Does not break the current api and preserves the centered alignment as default.
fixed render group example
fixes predicted position bug when animation dispatch has not occured yet
decoupled AnimationTiming from AnimationPosition
Merge remote branch 'manu/group_alignment'
default cell realizer
not sure how it could work in the first place
(maybe it worked due to a fortunate racing condition with pred)
using default realizers and help messages