Separate target from circuit #123
Description
What should we add?
Right now in the circuit object there is an optionally bundled target object. This really doesn't fit with Qiskit's data model as their independent data types that represent different things. The target is the software model of a QPU and it's constraints, while the circuit models the unit of computation on a QPU. I'm not clear why this is needed bundling is needed; I assume the intent was to track details about the compilation target after the transpiler is called but I would argue there are better ways to track this in user code and bundling the target just confuses matters.