Create Solr plugin for Indigo based similarity queries

[MysterionRise]

At the moment there is a Solr plugin, but:

• it's for old version of the Solr 5
• it's using ineffective reading of the stored field of the documents

Requirements would be:

• make it available for fresh version of Solr
• create optimised Scorer in order to battle limitations of this
• add support for different (potentially pluggable) similarities - Tanimoto etc, so results from the Solr would be already having it

[MysterionRise]

@AlexanderSavelyev @mkviatkovskii thoughts on this?