feat:dashboard aggregations

[NicoPL]

DONE:

• deal with data series (eg. relative_abundance)
• workaround to split data that is merged into rainfall+wind and couv_slope+cover
• configuration dictionary where is written what function to apply to each field
• write the right formula to compute standard errors within the MRP function

STILL IN PROGRESS:

• write other aggregation functions (SRS, SS, etc.)
• write other aggregation functions (total and proportion)
• get the year in meteo.csv to map with data and get population_size
• use 'project' as a new field to make clusters
• reorganize files:
  • make a constants.py to store constants and configurations of aggregation
  • keep in stats.py only the functions to compute aggregation
  • put in models.py the objects dealing with data and calling aggregation functions