Disable validation of Session Annotations until all code supports it

This was causing failures in "/webgl-viewer/stack-save".
Merge branch 'session_annotation_validation'

* session_annotation_validation:
  Disable validation of Session Annotations until all code supports it
Better stack interpolation, and correcting errors
Merge branch 'stack-annotation'

* stack-annotation:
  Better stack interpolation, and correcting errors