adding Fastq.convertTo(FastqVariant) and supporting methods

[heuermh]

Adds support for explicit conversions, e.g.

// illumina --> sanger variant conversion
FastqReader reader = new IlluminaFastqReader();
FastqWriter writer = new SangerFastqWriter();
FileWriter fileWriter = new FileWriter(new File("sanger.fastq"));

for (Fastq fastq : reader.read(new File("illumina.fastq")))) {
  writer.append(fileWriter, fastq.convertTo(FastqVariant.FASTQ_SANGER));
}

Companion pull request to biojava/biojava#334. As it is not convenient to use both 4.x and 1.x versions of biojava in the same codebase, the code in this package is mostly duplicated, org.biojava.bio.program.fastq here and org.biojava.nbio.sequencing.io.fastq in 4.x.

[heuermh]

@andreasprlic could I get this merged? The companion pull request biojava/biojava#334 has been. Thanks!

[andreasprlic]

sorry, missed this one.

[heuermh]

No problem, thank you, Andreas!