Simplification.

because the framework now sets self.outputs['returncode'].

Task #4052: Default settings (for now still in the tasks.cfg.in file) were set for the demix_always and demix_if_needed keys.

simplification of program loading

This is an intermediate update; appears to work well, is solid, but still some dipole dataset calibration attributes not set.
- add spectral mode support
  - new attributes still disabled: DAL update needed
  - not yet auto-flagging of lost/broken spectral frames: DAL update needed
- add parset for spectral test case, but test cases still disabled
- enable 64 bit offsets on 32 bit systems for >2 GB dumps, fix 32 bit build warnings
- add build option to write raw input to file to be able to retest without using a real station
- add input support for files and pipes for testing with flow control, apart from the normal udp input stream
- rename cmd line arg -p --proto to -i --input
- remove cmd line arg -r --rawdatafiles (now, external raw files only)
- improve exception handling
- use Storage_main's log prop file instead of our own
- fix cross-second boundary dumps, including correct output with (massive) frame loss
  - 1st spectral frame after crossing a sec boundary still gives crc32 error
- plug some mem leaks in error paths
  - 1 remaining, but difficult to fix and not grave
- fix writing of clock correction and offset attributes in the station group
- worker threads now report exit status to master, which propagates it into its exit status

Task #2669: Coherent Stokes beams with 1 station were registered as Fly's Eye beams in the LTA feedback

Task #1254: 'make install' now bails out with an error when byte-compilation of a Python source file fails during installation.