Refactor VepInterpreter.pm and add a new vep annotation filter

Refer to AT-628. For ACMG report, a new vep filter is needed to remove all variants that hit neither splice sites nor non-synonymous coding sites.
It might be better to make the vcf id a constant string rather than depending on the category list.  The exact categories can be gleaned from the description, but it will probably be easier for things parsing the vcf file if there is a single constant tag.