prepare for devise upgrade

 * minimum password length is 8: use '12345678' instead of '123456'
   for test cases
 * skip validation for default 'admin' account to keep 'admin' as
   password
move enum_fu plugin to lib/plugins; add generic lib/plugins initializer
use jquery/jquery_ujs from jquery-rails
prepare specs for upgrade
remove 'default_value_for'

 * didn't work with rails 4.0
improve secret handling with settingslogic
show devise flash errors and alerts
rails 4.0, update devise and other gems
customize style