Labeling of wastewater structures with multiple wastewater nodes #186

[sjib]

Description : According to VSA-DSS, a wastewater structure with a leaping weir is represented with two wastewater nodes see VSI-Wiki. This requires us to partition the input and output labels by NE.fk_wastewater_structure instead of RP.fk_wastewater_networkelement.

Additionally, I added two other enhancements:

1. Covers are enumerated
2. The enumeration index is only added if there is more than one input/output/cover.

Related issues :

• [x] https://github.com/QGEP/datamodel/pull/186#issue-1382622784

Related pull requests :

• [x] https://github.com/QGEP/datamodel/pull/186