Define schema update and deprecation process

[geoffturk]

When there is a new version of a schema available, schema creators should be able to require node operators to use the latest version when they create/update their profile using that schema. IOW, if v1 only requires name and URL, but v2 require name, URL and geolocation, v2 will be required to pass validation at the index.

Whether this should be a conditional requirement (specified by the schema creator in the metadata field) or required always needs some further analysis.

[geoffturk]

This is already implemented in MPG but it has not been implemented in the index.

[geoffturk]

• Define phases of obsolescence in the schema itself
• How are node operators forced to update in node interface
• In the Index, how does the nudging/forcing happen, if at all