Make S/N search in jira plugin configurable

* search_string is now specified in settings.py
* closes #74
Merge pull request #75 from rowanthorpe/make-jira-search-term-configurable

Make S/N search in jira plugin configurable
Improve app-path setting in Apache wsgi file

* Use var for easy app-path configurability/reuse
* Only append app-path to sys.path if it isn't already there
Fix copyright notice in Apache wsgi file

* update copyright year
* s/ISC/THE AUTHOR/
Improvements to Apache wsgi file (esp. maintenance mode)

* switch to maintenance mode when Apache is reloaded and
  "_maint_mode == True" (in non-maintenance mode server reload/restart
  has an infinitesimally small added cost of one var-assignment and one
  if-branch, but actual requests have no extra overhead at all - the
  "application" function is unchanged in the commit)

* set _app_path and _maint_mode vars at top of code and label them for
  editing

* label _maint_file at top of maintenance-specific code for editing (if
  a custom page is being used)

* add commented-out (non-default) version of maintenance mode handling -
  to dynamically handle maintenance page changes without
  server-reloading (but doesn't use inotify/etc, because doing that
  portably without sourcing Django libs is too complex to be worth it) -
  for speed-reasons, it uses global vars instead of arg-passing