vcfconvert: add vcf_to_hapslegendsample

* add vcf_to_hapslegendsample to vcfconvert
* output to stdout ir `-` or suppress with `.`
* change vcf_to_gensample to match the above
* fix some option parsing errors for `--tsv2vcf`
add tests for convert.

* failing the --tsv2vcf test at the moment due to bug parsing
  NULL (`--`) genotype. Should be skipping these lines, but
  printing with REF/ALT/GT from previous line.
add docs for new vcf_to_hapslegendsample
fix input path for `test_vcf_convert_tsv2vcf`
Merge pull request #114 from mcshane/feature/vcf2hapslegendsample

vcfconvert: vcf2hapslegendsample