LALInference to store command line in metadata and print it in postprocessing

Save the actual command line used in the dagman in the header of each output hdf5 files, for both nest and MCMC.

These appear in the header sections of the PP pages:

Nest: https://ldas-jobs.ligo.caltech.edu/~salvatore.vitale/test/O3/PE_Rota/S190425z/C01/IMRPhenomD_NRT_lowspin/1240215503.02-330564/V1L1/posplots.html

MCMC: https://ldas-jobs.ligo.caltech.edu/~salvatore.vitale/test/O3/PE_Rota/S190425z/C01/IMRPhenomD_NRT_lowspin/MCMC/1240215503.02-330564/V1L1/posplots.html

This updates and replaces request !1154 (closed) where I did end up with too many commmits.