GEOMESA-338,325,266 Scalding Ingest and Date Time fix.

This FCR branch builds upon GEOMESA-337, TSV/CSV ingest is now handled using scalding for both local and map reduce ingesting. Added fix for issues with date times being not properly ingested. The user is also now allowed to ingest data without date time information (the readme may need to be updated further to reflect this change). 

The scalding map reduce code breaks support for skipping the header in the file to be ingested, so this optional argument has been removed. 
It looks like this duplicates some of the code in @jnh5y 's https://github.com/locationtech/geomesa/pull/264 ...  Am I reading this right?