Implement queued search (prior to web deployment)

[joshuamonroe]

As discussed during the implementation of the search backend in #342, the current solution to enable realtime search indexing to make forum content searchable uses the realtime signal processor. This solution works well for low traffic applications (e.g. during dev) but an alternative solution, namely queued search, will become more appropriate when chigame is deployed to the web. See these links for further details and justification.

• https://django-haystack.readthedocs.io/en/latest/tutorial.html#reindex
• https://django-haystack.readthedocs.io/en/latest/signal_processors.html#realtime-realtimesignalprocessor
• https://django-haystack.readthedocs.io/en/latest/other_apps.html#queued-search