BibCatalog: new email ticketing backend

* Implements simple email ticketing backend.  Adds corresponding
  unit tests.  (addresses #872)

Reviewed-by: Joe Blaylock <jrbl@slac.stanford.edu>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibCatalog: default email backend

* Makes simple ticketing email backend to be the default ticketing system.
  (closes #872)

* Amends unit test case email address.

* Removes trailing whitespace.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
installation: help for BibAuthorID email settings

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>