LP#856708 - Scrolling/div size issues in action trigger interface

LP#856708 - Scrolling/div size issues in action trigger interface

The event definition content pane does not properly accommodate its contents.
In the Event Definitions tab, the list of event definitions exceeds the height of the
pane, but you can't scroll all the way down to the bottom of the list -- some of the
content gets cut off. Likewise, when editing an event definition, you can't scroll
all the way to the bottom of the page; the Cancel and Save buttons are cut off, and
you have to use the Tab key to move the focus down to those buttons, which forces
the pane to scroll to the bottom so that they're visible.

Signed-off-by: Jeff Davis <jdavis@sitka.bclibraries.ca>
Signed-off-by: Michael Peters <mrpeters@library.in.gov>