Require schemaVersion parameter in VitessceConfig constructor

[keller-mark]

User story

Want current code to stay compatible under future library versions. In order to identify the behavior that users are expecting, we need to know the view config schema version they are expecting compatibility with.

Preferred solution

Change constructor params to be VitessceConfig(schemaVersion, name = null, description = null) where schemaVersion is required but name and description are optional.

Possible alternatives

Put the version in the class name? like VitessceConfigV2 but this does not seem elegant