Test automatic migrations

[tantaman]

• If client upgrades and server is not upgraded, all sync connections should be terminated and no new ones established
• server should migrate on restart if new schema file and version is available
• client should migrate on restart / refresh under same conditions

[tantaman]

Auto-migrations work well other than the fact that we do not tell the user why a migration failed.

This is a really confusing experience as a user might add a required column to a table which already has data. This will fail but it isn't entirely obvious that it would fail.