[DS-1460] Add a new file for Solr messages to the log4j configuration
After discussion, raise loglevel and set a default limit on number of logs retained.
Merge pull request #268 from mwoodiupui/DS-1460

[DS-1460] Add SOLR logging config file
This merely adds a log4j appender for Solr's logging which will be used by the next release of dspace-solr.