Adds group support to the core search API and the Solr search engine.
This allows for:
* User searching by group (in the API only, no interface yet)
* Automatically restrict search results by group (in some cases like
separate-groups forums)
Introducing both APIs in moodle along with:
- search_box widget to add a tiny search box
- admin settings with setup steps helper
- cache for search results
- template for a search result
- php unit stuff
Many thanks to Tomasz Muras, Prateek Sachan and Daniel Neis for their contributions, for starting this development
and for pushing for it to be completed. Also thanks to other contributors: Jonathan Harker and eugeneventer.
sam marshall