Transition to ClinVar module output incorporated in `cancermuts`

[mtiberti]

We have incorporated what the ClinVar module does inside cancermuts, as a mutation source. Therefore we will, over time, deprecated the clinvar module.

As a first step of this, we need to make mavisp retrieve the information that was previously available in the clinvar module from the cancermuts module. We also need to retain compatibility with entries that still rely on having the clinvar module separately