MongoDB now available on develop branch

[sid-swirl]

https://github.com/swirlai/swirl-search/tree/develop
Tips for using it:

• Put the full mongodb:… URI into the credentials field
• The url field format is database:collection
• Copy/modify one searchprovider per Mongo collection
• Each collection to be searched needs to have a search index - we’ve only tested with default so far
• The SearchProvider query_template has to use single quotes; they are transformed to double quotes at query time
• Swirl reformats the Swirl query to ensure an “all match” search, "any" is not available by config, but is easy to do in code
• Use -term to exclude it from results. If the query is NOT term Swirl will rewrite it to -term for Mongo SPs automatically