Added admin/util/editable helper for easy inline editing

The helper makes it easy to create editable content on a page without
leaving the page and simply editing it inline with the save function
occuring over AJAX.

It uses the Jeditable jQuery plugin. The plan is to extend it with
support for additional input types and to include the WYSIWYG editor
among those types, but for now the types supported are:

- text
- textarea (which uses the jQuery autogrow plugin)
- select

For more info, see apps/admin/handlers/util/editable.php
Updated style of editable elements from admin/util/editable
Improved error handling in admin/util/editable and added more server-side logic to the example
Changed references from User to Member, which is clearer for non-technical users
Added delete button option and additional properties to admin/util/editable
Block groups can now have unit widths specified as unit-* CSS classes
Added alt, class and default image options to filemanager/photo helper
Merge branch 'master' of https://github.com/jbroadway/elefant