Copy primary header from input to output.

This fixes a bug that left output unable to be interpreted
properly by GBTIDL.
Fixed two bugs: bad velocity axis in FITS output, fail on bad procedure.

The velocity axis bug was the result of rebinned data no being
consistent with the necessary header keys.  The fix was to disable
rebinning in favor of higher resolution output.

The bad procedure bug was that the code assumed either OnOff or OffOn
procedures in the input for every target, even if not for every scan.
The fix is to no longer make this assumption.
Get spectral_pipeline back into a working state.
Merge branch 'spectral'

Conflicts:
	src/spectral_pipeline.py
Replaced pyfits with fitsio.
Added command line options and removed pyfits.
Warn when target and reference scans have different # integrations.

Before the pipeline would crash.  Now, it skips these scans.
Initial checkin of spectralpipe startup script.
Removed some command line options b/c this is not user-facing.
Check for OnOff/OffOn earlier. Limit number of output tables.
Added show_reduced.py script to create plots.  Fixed headers.
Fixed DATE-OBS bug to allow compatibility with GBTIDL.
Updated for EXPOSURE and DURATION in output.
Updated TSYS and TCAL to be an average over all scan in target spectrum.
Improved layout in show_reduced.py
Added showreduced script to make plots from spectral output fits.
Made showreduced executable.
Fixed typo in python script name.
Show data in velocity instead of channels.
Added gbtidl version of spectral pipeline code.
Conversion of spectral pipe to idl nearly complete.

Only need to check for restfreq==1420 and
procname==onoff or offon.