Move to standard upgrade mechanism

[OhRobin]

• Changing cockroach version via the the command dcos cockroachdb update start --options=update.json should not happen.
• A universe package should be tied to a particular version of the base tech.
• End users should not be able to set a URI

[triclambert]

Specifically, this option should not be exposed to the end-user: https://github.com/mesosphere/cockroachdb/blob/master/universe/config.json#L30

The version should be baked into the package, and exposed via the version string, such as 1.2.3-1.0.5 (<fw version>-<base tech version>).

/cc @a-robinson