Added property oxalis.jdbc.dialect to GlobalConfiguration
Made RawStatisticsRepositoryJdbcImpl and abstract class
Created RawStatisticsRepositoryMySqlImpl which inherits RawStatisticsRepositoryFactoryJdbcImpl and implements the MySql specific queries earlier found in SQLComposer
Removed SQLComposer
Changed RawStatisticsRepositoryFactory to return an instance of RawStatisticsRepositoryMySqlImpl instead of RawStatisticsRepositoryFactoryJdbcImpl