bloch redfield tensor with c_ops

Added ability to include collapse operators in the bloch redfield tensor generation.
I agree that the docstring for args was completely misleading. Sorry about that. But in general, args is there as a general placeholder for possible "extra stuff" that a user may want to pass to the solver, and should be present for possible future usage. Thinking about it now, args should probably be passed as extra argument to spectra_cb callback functions to allow users to give extra parameters to such user defined functions.