Added annotation interface

An annotation interface for capturing data to be indexed by Solr was
added.
Solr indexer creation, indexing annotation usage

The indexer that sends created documents to the Solr server by using the
created annotations was implemented. The annotations for POJO fields
indexing were used in several classes.
Solr indexing tests created.

Tests covering sending created documents made of different POJOs were
created in order to demonstrate the indexer functionality.