TST Folder Expand Collapse per dsl101

TST 'Folders' (e.g. URLs of the form moz-extension://[TST-Ext-ID]/resources/group-tab.html) are toggled (expand / collapse) when clicked, instead of being activated. Regular tabs which have children will do the same when CTRL+clicked.

You can 'activate' a folder tab in order to rename it by CTRL+clicking on it, editing the title at the end of the URL, then CTRL+click again to 'discard' it. In addition, folder tabs can't be accidentally closed by clicking the close icon; they can only be closed after being activated by CTRL+click (note even then, this doesn't close children, only the folder).

TST normally tries to move focus away from a tab when it's folder tree is collapsed; this is disabled when using this add-on, so that the active tab can remain active even when the folder tree is collapsed.

When hibernating a tab, TST tries to focus & activate the parent. This is disabled when using this add-on, and the next previous active tab is focussed instead. This prevents 'folder' tabs from becoming activated when hibernating their children.