Renamed the VCF module
Changed default VCF projection into a 'cohort' one

This particular projection combines VCF information for the whole
cohort.
Refactored VCF module to be able to use VCF data in export.

This also included refactoring the cohort level computations
into a separate class
Refactored the cohort statistics out of the VCFDataRow
Added extra reference/alternatives methods to cohortStatistics
Added referenceAllele to allDataProjection
Whitespace
Bugfix in variant projection
Added tests for variantprojection, as well as for VcfData object
Adjustments to the Vcf tests
Added test for VCF all data projection
Altered cohortprojection to only return necessary fields
Improved and simplified test to cover the right things and only those
VCF projections now specify the fields to be retrieved from the database
Small improvements to VCF tests
Removing unnecessary checks in projection tests
Removed redundant checks
Minor improvements
Merge pull request #44 from thehyve/features/FT-711-extend-VCF-module

Refactored VCF module