Great start Rated 5 out of 5 stars

I have a couple of ideas for you moving forward. Rename it to AppTab+ and start adding new features for manipulation of AppTabs and their views. First new thing that I believe should be added to complete the functionality of an AppTab is to block the use of an AppTab for the opening of any URL which navigates outside of the AppTab's set domain. This works currently for clicking a link in an AppTab, but should also extend to clicking of a bookmark from your toolbar or entering a URL manually (in the case of your refined view, through the Alt+D command).

This review is for a previous version of the add-on (0.9.1-signed.1-signed).