Bug 908329 - [Keyboard] Update alternatives menu width logic. r=djf

Update German keyboard alternatives order and make the first alternative
character at least the width of the key it is an alternative for, thus
ensuring it is the first one selected when tapping on sides of the key
that shows the alternatives popup.
Merge pull request #11794 from mcirlanaru/bug_908329

Bug 908329 - [Keyboard] Update alternatives menu width logic. r=@davidflanagan