Added new DBConnMetaData class and changed classes accordingly

Consumer implementation now passes serialized DBConnMetaData object
along the stream rather than crudely having an open JDBC connection
passed to StreamTasks.
Changed from using DatabaseConnectionMetaData to DatabaseReaderParams

Both classes did essentially the same thing, so optimised it by making
DatabaseReaderParameters a serializable class and putting it onto the
SystemStreamPartition in the Consumer implementation.
Moved Parameters class to util package

Updated references to Parameters class accordingly.
Merge branch 'db-test' into database-reader

Conflicts:
	samza-wikipedia/src/main/java/samza/examples/databasereader/system/DatabaseReaderConsumer.java
	samza-wikipedia/src/main/java/samza/examples/databasereader/system/DatabaseReaderSystemFactory.java