Update methods around gauges

[hboisgon]

Based on several open issues, this PR contains several changes associated to gauges:

• split setup gauges and outlets in different setup methods setup gauges with upstream area snapping #170
• add a create_gauge method to add gauge directly from a gpd.GeoDataFrame
• add a setup_config_output_timeseries to be more flexible in adding new varibale/column for netdcf/csv sections of toml
• updates on how to derive outlets fixes create workflow methods + unit tests for setup_gauges functionality #76
• support gauge data type geodataset fixes setup gauges based on a geodataset  #85
• support changing snapping distance fixes Add max-snap-distance option in setup_gauges #68
• support snapping gauges based on upstream area fixes setup gauges with upstream area snapping #170
• add unit test create workflow methods + unit tests for setup_gauges functionality #76

[hboisgon]

I think this PR is more or less ready to be merged. Because I added a new create_gauges method, I wonder if we include it in the next release or wait for this issue to be fixed in hydromt core before merging: Deltares/hydromt#312

[laurenebouaziz]

Really nice work @hboisgon !!!
I have only some very very minor suggestions, more in terms of additional details in the documentation.

I tested the new snapping option based on area using data from a project and it works very well, nice implementation! also great that there are now more possibilities for the gauges_fn format.

the tests are also running for me, so I think after checking these minor comments, it is ready to merge!

[hboisgon]

Hi @laurenebouaziz ! Thanks a lot for the review! I added better docstrings, you were absolutely right :) and I answered some of your questions here too. Could you re-review and see if the changes I made are good?

[laurenebouaziz]

thanks @hboisgon for the clear docstrings and all the explanations to the questions I had, all clear to me. Apart from the last tiny comment, I think it is good to merge!

[laurenebouaziz]

Great, thanks @hboisgon for all these nice new additions!