Separate logical and physical qubits

[ecpeterson]

We've recently had to resolve a bug that would have been caught if CL-QUIL were somehow aware (e.g., through its type system) of the distinction between logical and physical qubits, rather than treating them both as undistinguished integers.

There's almost an opportunity to implement this tagged conversion through the rewiring API, but the rewiring API currently takes unboxed integers (rather than qubit objects), which don't admit easy tags. I'd propose re-boxing these and distinguishing between the two cases in the same stroke.

CC @notmgsk