Improve search logic and allow search of event archive (#248)

* Added search to person, venue, organisation and event archive

* Added search to invoice archive

* Added event search to homepage

* Tidy up event search logic and optimise

* Fixed merge issues

* Stopped 404 on failed search

* Set default ordering of people, organisations & venues to alphabetical (rather than order of addition to database)

* Added invoice search to home page (if you have permissions)

* Made invoice archive sort by reverse invoice date (rather than order added to database)

* Added search help page (very pretty)

* Made single search box for all search types

* FIX: Missing date field breaking archive view

* FEAT: Add omnisearch to header

Tis a bit broken on mobile at the moment...

* CHORE: Conform old code to pep8

* FIX: Select the event form, not the search one in tests!

* Revert "FEAT: Add omnisearch to header"

This reverts commit 6bcb242d6b because it caused MANY more problems than anticipated...

* FIX: Stop 404 on failed search, again

* FEAT: Basic testing of search

* Use a tooltip to help explain the UX

Obviously since it needs a tooltip it isn't brilliant UX but the best I can think of for now...

Co-authored-by: Tom Price <tom@codedinternet.com>
Co-authored-by: David Taylor <david@taylorhq.com>
Co-authored-by: Arona Jones <aj@aronajones.com>

RIGS/urls.py

@@ -21,6 +21,8 @@ urlpatterns = [
 
     url(r'^user/password_reset/$', views.PasswordResetDisabled.as_view()),
 
+    url(r'^search_help/$', views.SearchHelp.as_view(), name='search_help'),
+
     # People
     url(r'^people/$', permission_required_with_403('RIGS.view_person')(views.PersonList.as_view()),
         name='person_list'),