Refactor state distinguishability and add routine to check if perfectly distinguishable

[vprusso]

It seems like using picos is often preferable for solving SDPs in quantum information. It would be ideal to do the following for the state_distinguishability.py code:

1. Refactor from cvxpy to picos.
2. Remove usage of the state helper code as this is unnecessary bloat we should eventually remove.
3. Add function is_distinguishable that allows one to determine if an ensemble of states is perfectly distinguishable (i.e. has an optimal SDP value of 1).
4. Support both minimum-error and unambiguous discrimination strategies
5. Optionally, have functionality for implementing both the primal and the dual problems.

[vprusso]

This has been completed.