Show fallback account name on header bar when logged in admin

By default the admin header displays (where X is the nickname)

  "Logged in as X"

If the account does not have a nickname set it will be blank
and instead just show

  "Logged in as "

Do not assume nickname has been chosen yet and instead fallback
to either name, or if that is blank, login username. The last
is never blank.
Add missing language sections for admin layout view
Hide Display Name option choices in profile edit if blank

It's possible the user name options for setting Display Name
are blank or empty strings so let's check for that in addition
to if they're set in the first place.
Merge pull request #125 from randomecho/profile-display-name-setting

Display name settings in admin if left blank or empty