Fix problem with saving user settings birthdate.

BB-382 #close
Add an empty state to availability combobox.

BB-381 #close
Rename profiles.js/hbs -> users.js/hbs.
Add share time / knowledge and money checkboxes to settings.

BB-384 #resolve
Add username to admin page.
Merge pull request #361 from benkonrath/settings-tweaks

Profile and settings tweaks.