webstaff: add routine for Dojo JS to detect if running in iframe

webstaff: add routine for Dojo JS to detect if running in iframe

Sometimes legacy Dojo interfaces may need to adjust their
behavior if they're embedded in the web staff client. This patch
adds a new utility function, openils.Util.inIFrame(), to detect
if such code is running in an iframe. If so, the presumption
is that iframe belongs to the web staff client.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Jason Stephenson <jstephenson@mvlc.org>