Defaulting to --no-check-unique-key-change and --no-check-alter may be inappropriate for some users. Dropping these as defaults from OnlineMigrator makes it safer for first-time users and removes one limitation from the README.md. And those who still want them can still set those in their config or PTOSC_OPTIONS.

Since this would technically be a backward incompatible change it should also bump the major version number, if it won't already change for the next release.