Make the units of the sensing MCMC output be in units of seconds and not microseconds, decide on Q or 1/Q

This will change the values that are currently output, which may break existing tests or other codes. Also need to decide how to use 1/Q (current) or Q in the sensing MCMC and then how it is used in other places within pyDARM

See !132 (merged) for a kludge that needs to be fixed