This commit updates the plugin to the latest guidelines, as shown in
discourse-plugin-skeleton, which involves moving a lot of the code to
dedicated files, use proper namespaces, use the autoloader as much as
possible, etc.
Previously this was adding an extra AJAX request to check if the group had any queries available. Now a boolean is included in the group serializer, so there is no need for the extra request.
Removing this ajax request will also stop other plugin JS integration tests from failing when the data-explorer plugin is installed.
This commit also fixes the HTML markup of the tab, so that it doesn't have a <ul> nested inside the existing <ul>. Also adds an icon for good measure.
Loïc Guitaut
Bianca Nenciu
David Taylor
Jarek Radosz