Increase spacing between events in calendar view
Disable modal backdrop for newsletter and credits

The version of the boostrap-modal library we're using is broken and
there's no indication why; it fails to bring up the dialog and clicking
to get out of the modal causes all mouse-click actions to no longer be
recognized.  Disabling modal backdrop solves the issue for now.
Ability to control topics when creating a new source

Source inherits the organization's topics by default, but provides a form
field to add or remove them as desired.  Topics are saved with the source
so that future imported events inherit the associated topics.