Since, neither the slapos parameters and neither the Parameter Form can support the full scope of JSON Schema, we introduce a more restricted meta schemas.

Few examples:

• whenever you use XML serialisation, you cannot use "object" or "array", since all values are flat (as string).
• complex cases like "Any of" or "One Of", with complex sub-objects are unsupported by the parameter form. This isn't a problem for the instance itself, but since the form don't support it, it can lead to a bugged and unpredictable outcome.

The schemas might evolve (in case of json-in-xml), as long as the parameter editor evolves. Unsupported schemas just tend to failover to a text area.

/cc @romain @tomo @vpelletier