Appended this.id to the iframe id, so that each app has a unique id.  This was suggested by Dylan on the SAGE2 Google group to fix the problem of only the first instance of the app responding to pointer events.
Appended this.id to the iframe id, so that each app has a unique id.  This was suggested by Dylan on the SAGE2 Google group to fix the problem of only the first instance of the app responding to pointer events.

sliceresearch/usc_sage_biodigital