Fe stream test upgrade - simulating large numbers of fe for daqd testing

fe_stream_test is a single front end outputing a rmIpcStr to mbuf.

fe_multi_stream_test can be used to simulate fe systems in bulk, it outputs to a dac_multi_cycle_t in mbuf, along with populating a ini directory and master file. This is targeted for daqd development and testing.

This adds a fe_generator_support library which holds some common code between the two generators.

This also adds another check to fe_stream_check, verifying the data crc.