Allow for manually correcting HGVS Notation/Call for an annotated variant

[xiamaz]

Is your feature request related to a problem? Please describe.
Some variant calls might be incorrect or need to be adjusted to take multinucleotide variants into account. Currently the user might change their HGVS annotation string in a report or another place

Describe the solution you'd like
Corrections to HGVS annotated small variants or ISCN annotated structural variants should be storeable in a variant annotation, so that solution variants can be properly annotated and stored in Varfish. Otherwise a lot of structural variant annotations might be incomplete or not be able to include information from downstream validation.

Describe alternatives you've considered
Having another system storing this type of information. This is currently done in baserow or might be the role of another lims.

[holtgrewe]

Also requires updates to baserow ETL scripts, thus would not be as helpful as needed right now. Postponing.