Full text search by Solr

Adds full text search feature with Solr - issue WAVE-311.
To test either setup your own Solr instance or use the ant target:   
ant get-third-party-solr-dep
This will download the Solr version 4.9.0 into third_party/solr and unzip it.
Then you can use the run-solr.sh/run-solr.bat to start the Solr server.
This patch also hopefully solves the issue when inbox counters are not updated (WAVE-371).
This can be very slow. Is not it better to keep the digest in the index?