show GeoNode version and API client capabilities on the GUI

[ricardogsilva]

In order to provide support for different GeoNode versions, the plugin uses different API client classes. These have different capabilities, which in turn limit what features are enabled for each connection (e.g. a GeoNode server that has version 3.1.0 uses an API client class which is not able to upload QGIS layers as new GeoNode datasets).

Lets surface this information in the connection management dialogue. This will allow end users to understand why some GeoNode remotes may appear to be better supported by the plugin.

[ricardogsilva]

This has been implemented in a recent PR,l so closing