draw heterozigosity per sample plot implemented
New filters created: MissingGenotypesFilter, AlleleNumberFilter,
GenotypesInSamplesFilter, GenotypeQualityFilter
Merge branch 'master' of
ssh://gitolite@proxybioinf.comav.upv.es:2203/vcf_crumbs

Conflicts:
	test/test_vcf_filters.py
	vcf_crumbs/vcf_filters.py
histogram for missing call percentage per SNP added
histogram for number of SNP per reference seq added
function to calculate number of bases covered by reference seqs with
SNPs in vcf implemented and added to draw_snv_stats
Option to select samples in draw_snvs_stats added. Samples names are
given in lines of a text file
error in (strip() added to remove \n from sample names) reading sample
files fixed
Typing error corrected
Missing calls percentage shows now the actual amount of missing calls
instead of called ones
num_diff_to_ref_gts now counts both heterozygote and alternative
homozygote
Simplification in code of calc_n_bases_in_chrom_with_snp
binary for new filters implemented
typing error fixed
error when parsing genotypes fixed
test for bin run_vcf_record_filters added
AlleleNumberFilter and MissingGenotypesFilter can now take into account
only a set of samples given by user.
GenotypesInSamplesFilter will not filter out records if genotypes are
uncalled. 
Option to set a min number of called genotypes for this filter
implemented. If it is set to the number of given samples, it will work
like the previous version
New plot added: call density per number of counts of each allele split
into homozygote and heterozygote according to snp caller
Drawing maf distribution per sample is optional now