Search plugin

This is a search plugin that modifies and combines code from two projects:

Sphinxcontrib-lunrsearch (https://github.com/rmcgibbo/sphinxcontrib-lunrsearch) - the lunr-index generation component was reworked to read more than just the api and addded supoort for using the lunr python library to pre-generate the search index.
Mkdocs lunr search (https://www.mkdocs.org/) - the javascript components with web-worker support, using the index generated by the above module.

Parsing of the documentation to create the index is custom.