Merge pull request #20 from PatrickDeelen/master

Genetic variant plus small improvements
Merge pull request #21 from PatrickDeelen/master

Remove old, more tests, improve variant
Merge pull request #22 from PatrickDeelen/master

Removed getSnpRefAllele()  and work in progres modifiable
Merge pull request #23 from PatrickDeelen/master

Added cache size property for variant providers and work on modifiable genotype data
Added impute2
Merge branch 'master' of https://github.com/molgenis/molgenis-genotype-reader

Conflicts:
	src/main/java/org/molgenis/genotype/vcf/VcfGenotypeData.java
Impute2
Merge pull request #24 from erwinwinder/master

Impute2
ModifiableGenotypeData work in progress
Merge with erwin