Fixes and minor features

Added a bunch of minor features and fixes:

• CDO pp: do not overwrite output files unless explicitly specified
• CDO pp: will not add output files multiply
• CDO pp: merge (and other operators) possible now, using input-file derived patters for further input files
• CDO pp: empty dict for no variable selection possible
• The variables (-groups) that are continued within a reinitialization are now configurable.
• Logging slightly improved.
• Licensing of used tools (e.g. Autosubmit, SAMOA, CDO) is highlighted.

Closes #137 #144 #149 #150 #151 #152 .