Adding Solr operator:

1. Input Operator: Reads data from Solr server based on user defined queries.
2. Output Operator: Writes data to Solr server.
3. Unit tests which uses embedded Solr Server.
4. resources file which needs to initialize embedded solr server for unit testing.
5. Demo app for Solr Input and Output operator
Not used anywhere right now. Have provisioned it, in case someone using this operator needs it.