Implement Solr language mode

Implements a simple Lucene/EDisMax query language mode. We've found it very useful for query highlighting for advanced users.

I just kinda imitated the other language modes' setup - if I should structure it differently, please let me know.

Lucene / Solr query examples:
http://lucene.apache.org/core/2_9_4/queryparsersyntax.html
https://wiki.apache.org/solr/SolrQuerySyntax