Load and display GeoJSON multipolygons for assets

[MathiasBaumgartinger]

First a request to load all the assets from the server needs to be implemented. These will fill the ui_controller.gd script. Once loaded when choosing an asset a GeoJSON multipolygon should be drawn to see where the asset can be placed. This will be shown until leaving the edit mode.

[MathiasBaumgartinger]

Assets-JSON requested from server now and loaded into the UI. Probably needs some tweaks and functionality.

[MathiasBaumgartinger]

Now does everything like it should, the problem is the itemSpawner gets set the according item id. For me locally the itemSpawner does not spawn items however.

[MathiasBaumgartinger]

Need placement arreas to continue with work.

[chrisgraf]

the real data is still in preparation .. can you add a dummy fixture?

[MathiasBaumgartinger]

WorldPosition.get_position_on_ground(vec : Vector3)

With this function the required y-axis for a given Vector3 with proper set x- and z-axis can be found.

[MathiasBaumgartinger]

Added dummy fixtures, will continue work once real data is there :)

[chrisgraf]

We probably need to enhance the given code to also cope with point data

we will not implement point data for 0.4

[chrisgraf]

missing issue is the check if the overlay is above the surface

[chrisgraf]

this is moved and discussed further in #31 so closing this as duplicate