Add new friction types to cross_section_location

[leendertvanwolfswinkel]

Currently, we have two friction types, Chézy (1) or Manning (2)

Two new friction types will be introduced, valid only for cross_section_location:

• Chézy with conveyance (3)
• Manning with conveyance (4)

Please update the value maps for the attribute friction_type with these values.

Please keep these changes on a separate branch until we have released these new features on the server

[leendertvanwolfswinkel]

@ldebek Can be merged now!