Initial qgis test plan

[deltamarnix]

An initial QGIS test plan for the plugin. There are still some tests to be written.
I have also performed all these tests and created quite some new reports.
There is also a known issues page for all of Ribasim, as we have some things that simply don't work as expected.

New issues:

• QGIS plugin has enabled buttons when no model is loaded #1678
• Creating a new model with QGIS in the same folder errors the plugin #1679
• QGIS overwrites toml files on New #1681
• QGIS plugin not emptied on new project #1682
• Can add a layer twice to the QGIS model #1683
• Deleting Edge layer from a geopackage makes it impossible to open in QGIS anymore #1684
• Error when adding the same table twice in QGIS #1685
• Adding nodes in QGIS lets users add the same node_id multiple times #1688
• Edge snapping is performed after saving layer in QGIS #1689
• Go back to globally unique node IDs? #1690

Fixes #320

[visr]

We should also include the layer styling: #1748 (comment)