First step to minor allele frequecies

Does not work at the moments. Needs the genotypes.
gitignore update
Merge pull request #1 from PatrickDeelen/master

Minor allele frequecies part 1
Small changes, discussed with Patrick
Merge branch 'master' of https://github.com/molgenis/molgenis-genotype-reader
Added SnpGeneticVariant.getSampleSnpVariants()