Warn on incompatible schemas

[waldekmastykarz]

Now that we aligned versioning schemas with proxy versions, we should show a warning when the user tries to load a config file that uses a schema with a different version than the current proxy version. The warning should include a download link for the corresponding release. In the v0.x range, let's not assume backwards compatibility and check for exact match.

[garrytrinder]

We currently have this in the Dev Proxy Toolkit where we check that the schema version matches the installed version of Dev Proxy and show a warning if they are not the same. Additionally we provide a code action to update the schema version to align with the installed version. This currently is only applied to config files, so we should expand it other files that contain a devproxy schema.