move My Submissions to primary nav (bug 860373)

Note that only comment #13 (https://bugzilla.mozilla.org/show_bug.cgi?id=860373#c13) is relevant. The discussion around this minor issue got a bit out of hand and was reined back in.
The idea is to not include "My Submissions" twice, and thinking we probably shouldn't include "Submit an App" twice either (down from three times!).