Add support for Delly2 CNV and MELT

[holtgrewe]

Is your feature request related to a problem? Please describe.
We do not explicitely support Delly2 CNV and MELT.

Describe the solution you'd like
We should support them.

• add explicitely to supported tools
• add test cases
• document as supported tools

Describe alternatives you've considered
N/A

Additional context
N/A