Feature: AutoJoin Tables

[frida-161]

Right now the GMLAS import detects the relations in the database and creates these in QGIS.
The relations get categorized as either 1:1 or 1:n relations.
For a customer we would like to add the option to auto join the 1:1 relations on the geometry layer.
This way they can work with all the available data right after importing the WFS through GMLAS without any extra steops.

I would propose this to be and optional feature, that can be accessed through a Checkbox in the GMLAS Import dialog.