Include filter option for suitable image pairs based on weather conditions

[loreabad6]

Suitable image pairs are now found in 1_find_suitable_pairs, based on Sentinel-1 metadata information and baseline between master/slave pairs.

IT would be good if we could include information about weather conditions during acquisition. Possible sources are CHIRPS data.

See also: https://github.com/SliDEM-project/project-management/issues/10