Support double occultations netcdf files

Double occultations would have different dimension names than usual.
The code now figures out the original dataset dimension names for proper initialization before renaming to the human readable versions "pixels", "wavelengths" and "times".

Pre-release of UVIS tools

Most of the data reading works for me but the S/W needs to have more eyes on it, so I create this release for a wider dissemination.