SSB-47: fixing nan error in computing the std deviation and using the proper hierarchy to get the beam string

SSB-47: improved logging and skipping the regex check for directories with a nesting level higher than 2 (hence all the files that compose the MS).

SSB-47: including calibration table used for the observation and the one derived after the holography calibration

- included function to load from hdf5 file
- error handling when loading from file
- frequency axis generation
- derive new calibration table from existing one
- relative tests

SSB-47: parsing header values and implemented read function to obtain a dict object with the station and mode as keys