Retrieve glaiciers by major river catchement

[yweidmann]

Implementing a method to retrieve glaciers based on the major river catchments:

• Rhein
• Rhone
• Aare
• Limmat
• Reuss
• Ticino
• Inn and Adda

Definition of the catchments by own classes or enumerations.

As parameter a list of catchments has to be defined. This will allow to retrieve glaciers from multiple catchments.

[yweidmann]

Regarding the complex SQL statement for some of the catchments a static list of predefined catchments has to prepared. It will also simplify the usage.