Please make it possible to run multi-visit cosmic ray rejection on H4RG data

Currently the multi-visit CR code is disabled for H4RG data. In general this is probably correct, as we can do a very good (better?) job by looking at the up-the-ramp integrations. However, this comes at a significant cost in time (c. 25% of the total integration time), and we may not want to pay this cost on the mountain.

Please add config options (and supporting code!) to control this.