19-add_waterregions_utility

[StefaniaGrimaldi]

This pull request is linked to the issue #19 Add utility: water regions map.

Two scripts have been added:

• define_waterregions allows to create a water region map which is consistent with a set of calibration points;
• verify_waterregions allows to check the consistency between a water region map and the map of calibration catchments (this package must be used only when the water region map has been created without using the script define_waterregions).