New flagstat command. Upgrade to Parquet 1.2.5. Reference ID bugfix.

o Added a new flagstat command which write ADAM stats identically to samtools flagstat
o Upgraded to Parquet 1.2.5
o Fixed bug where the mate reference id was being written to the read reference id
o Created a new ADAMRecordField enum to help prevent typos in code with literal strings
o Added log4j.properties file to turn down logging in local mode