Fix cancer RankScore VCF load and STR next

[4.7.3]

This minor update - possibly the last before switching to bootstrap4 - includes the following highlights:

Added

• RankScore can be used with VCFs for vcf_cancer files

Fixed

• Fix issue with STR view next page button not doing its one job.
• Fixed mitochondrial report bug for variants without genes

Deleted

• Removed pileup as a bam viewing option. This is replaced by IGV