Check and complete the data validation sections

[jdreo]

The adapter files now includes a validate section that specify checks on the data.

For the DECIDER-related adapters, those validation scripts are derived from the explanations put on the DECIDER wiki.

However, in their current form, some explanations are missing and some assumptions about the data requires double-check, as they seem inconsistent (some values do not exist in the actual tables, some seem at odd with the expected values, etc.)

Related files are located in oncodashkb/oncodashkb/adapters:

• copy_number_alterations.yaml (for "external" data)
• copy_number_alterations_local.yaml
• single_nucleotide_variants.yaml
• single_nucleotide_variants_local.yaml
• oncokb.yaml

The task is to browse the validate sections of those files and fix everything that's marked with a "FIXME":

1. Add explanations about the expected data as comments, replacing the "#FIXME: not present in data declared in source description." ones.
2. Double-check the validation constraints (data types, and most notably: possible values).
3. Add more validation checks if needed (the more, the merier).