Common channels should support parameterized values

[dabacon]

Right now they are just floats (missing type info). Generally these should be parameters at is very common in simulation to want to run the channels for different noisy rates.

[jfold]

Any progress on this? Especially for AsymmetricDepolarizingChannel, a parameterization would be awesome.

[balopat]

@jfold no progress yet! We'd be happy to accept a mini design here & a PR.