Merge all the CC

[halvarsu]

It would be very nice to autogenerate the subclasses of CC, building the subclasses using a fixed set of diagrams based on the name (i.e. "CCSD" automatically gets singles and doubles amplitudes and the correct diagrams). This is especially true in the time-dependent case where most functions are basically the same (up to the number of amplitudes etc) between truncation-levels.

Note, this is a convenience issue, not a performance issue.