Allow user to dial in manual offset for recorded piece

[seanmtracey]

While we do out best to reduce latency and line up as many recorded pieces as best as possible, there will be times where we get it wrong.

To lessen the possibility that a bad offset will be set by our systems, a manual override will be included which will derive its value from our algorithm, but will enable the user to override it if it's not to their liking.