Add paired-fastq writing functionality

- converting read to FASTQ optionally adds suffix

- opt. verification step when reading paired-FASTQs

- add method for outputting paired-FASTQ files

- add persistence to paired FASTQ writing

- round-trip test of paired-FASTQ reading & writing

- add bam2fastq command for outputting paired-fastqs

- rename bam2fastq to adam2fastq

- use ValidationStringency in Adam2Fastq

- adam2fastq asserts equal #s of first-/second-reads