Revision 4110

backport (sh002i): improvements to URL handling.
* use use_abs_url option of systemLink to generate URLs, rather than
hardcoding logic.
* don't generate a full URL for the return to your work link. it isn't
needed.
* in the "This feedback message was automatically generated by the
WeBWorK system at" message, give the URL to the webwork home module,
rather than just the host and port.