3.1.0

This release adds the read/write state callbacks to psp.Pv, with sensible defaults that keep pv.read_access and pv.write_access booleans updated. These are each set to True if we have the respective access to the PV, and False otherwise. You can use pv.add_rwaccess_callback to add a callback to be run when the read/write access of the PV changes.

Thank you @mattgibbs for contributing this feature, now both in the pyca and psp layers