- to revert to the default step sizes (those used pre-this patch)
    this relies on the structures CoherentGW and PulsarSignalParams
    being initialised with dtDelayBy2 and dtPolBy2 set to zero. For
    all codes that uses these it has been check that this is true, or
    otherwise edited in this patch.
  - RP: added minor readability improvements to the patch, otherwise OK.
  - set the dtDelayBy2 step size to 10 seconds in the pulsar software
    signal creation routines create_pulsar_signal_frame and
    sw_inj_frames
  - closes #676
Original: 65fa695b05b8e24f7dc49742bed43be3a7bc8c80