TextView: Update nav shortcuts again

Make Cmd+Left and Cmd+Right work the same as Option+Left and
Option+Right, that is, they do word-wise navigation.

Make Option+Up go to beginning of paragraph and Option+Down go to end
of paragraph like Cmd+Left and Cmd+Right used to.

Unfortunately option shortcuts are currently eaten by S&T until #9431
gets fixed.
Mail: Change quote and unquote shortcuts

to Cmd+' (quote) and Cmd+Shift+'

This should also work better for International users who don't have
ready access to the [ and ] keys.