Move solr configuration in the conf folder

This way it's possible to use org/sakaiproject/search/solr/conf as
SOLR_HOME
Rename solr.search.data.dir to the default solr.data.dir
Use NRT directory with solr 4.1
Reposition abortOnConfigurationError
Use the default configuration for the select path
Replace deprecated XmlUpdateRequestHandler with UpdateRequestHandler
Enable the high-performance update handler