Check that OMC compensation filter values are working properly

There seem to be a couple of issues with the OMC compensation filters in the ini configuration files that are not working properly.

• check that users can put in a filter file, bank names, modules in use and gain in a variety of combinations of being available or not as key-value pairs that don't cause the DARM loop model to break
• Non-unity gain values in omc_compensation_filter_gain currently results in changing the overall optical plant gain. Example: a value of 1000 results in an optical plant model with gain of 1000 x coupled_cavity_optical_gain. Optical plant should not be impacted by the compensation filter gain