Add non-standard and non-gregorian calendar support for Saving Module

See merge request es/auto-s2s!22

Merge branch 'dev-saving-add_calendar' of https://earth.bsc.es/gitlab/es/auto-s2s into dev-saving-add_calendar

Handle missing values in skill metric arrays in Saving module, fix bug in compute_probabilities()

See merge request es/auto-s2s!21

Decadal case improvement

See merge request es/auto-s2s!20

Merge branch 'dev-decadal-user_feedback' of https://earth.bsc.es/gitlab/es/auto-s2s into dev-decadal-user_feedback

Add Saving module to the suite and merge several improvements to other modules

See merge request es/auto-s2s!19