Allow for flexible time frequency in climate forcing

[dsgoll123]

Current: the tool requires 6h climatic forcing and it compute time aggregated (monthly, annual) statistics of the climate variables.

Goal: Allow for other frequencies (e.g. 3h & daily) of climatic forcing commonly used with ORCHIDEE

[dsgoll123]

see for some earlier characterisation of problem and potential solution in issue : Possibility to read daily climate forcing for ML #17

[dsgoll123]

A agent is working on it: https://github.com/CALIPSO-project/SPINacc/tasks/ee5ee69c-e85d-402b-90c3-cc8e75b26960