cleanup, dependency in adminSettings, start UserPrefixPin

- cleaned up array declaration in adminSettings.php
- added dependency system for config options in adminSettings thus options may only show up when their dependencies are solved
   it's implemented using JS, CSS and HTML classes.
   each option may have the attribute 'classes'.
   if the class 'hidden' is added this way the option will be hidden using CSS (default CSS of ownCloud).
   if the class 'hasDependency' is added the option will get 'padding-left: 25px' using CSS provided by css/styles.css
   for checkbox:
     if a checkbox is toggled every element with a class which equals the 'name' attribute of the checkbox will toggle the class 'hidden' (add if not present and remove if present)
   for select:
     when an option of a select is selected:
       - the class 'hidden' will be removed from every element with a class concatenated by the 'name' of the select, the string '_' and the 'value' of the selected option
       - the class 'hidden' will be added to every element with a class concatenated by the 'name' of the select, the string '_not_' and the 'value' of the selected option
     example:
       <select name="foo"><option value="BAR">BAR</option></select>
         will result in the classes 'foo_BAR' for which 'hidden' is removed and 'foo_not_BAR' for which 'hidden' is added
- added save notifier which is shown when a setting was saved successfully
- started correct implementation of UserPrefixPin as intended by multiotp-class
  - added new option 'UseUserPrefixPin' to indicate whether a pin should be prefixed
  - added new option 'AllowUserPrefixPinOverride' to indicate whether users may overwrite the default pin

Signed-off-by: Andrwe Lord Weber <lord-weber-andrwe@andrwe.org>