Add a min-coverage filter
Move encode and decode methods into bam-readcount entry
min coverage filter passes when coverage is greater
sample index will always be an integer
Min coverage filter fails if coverage level not met
Add validation tests to FTKeep filter
Move create entry into test helper
Export helper functions
Pull get_readcount_entry into base class

We will need this for everything that accesses
bam-readcount info from the vcf entry
vcf entry needs to use vcf genotype
Add vaf filter"
Die unless count is a number
Fails if the vaf is below the threshold
Merge branch 'updated' into gb_master