GSVar: Extend variant classification

[BeneKenobi]

We need to add additional (sub)information to the current classification system such as R for risk-allele or m for moderate/low penetrance variants.

[marc-sturm]

We already have that:

ngs-bits/src/cppNGSD/resources/NGSD_schema.sql

Line 703 in 041b2d1

`class` ENUM('n/a','1','2','3','4','5','M','R') NOT NULL,