- fixed bug where changing back to default content type or changing template caused fatal errors

- fixed a bug with smarty processing when saving a page

- fixed a bug with preview tab

- re-added expand/collapse button to toggle content blocks in backend

- added params editor_groups/editor_users to specify certain users/groups that are allowed to edit certain blocks

- removed params selected/checked; use param default instead

- block ids will be converted from block name using core function munge_string_to_url (to remove special chars, whitespaces, umlauts etc.)

- fixed bug of blocktype dropdown/select_multiple where first item had an empty label if only the param "values" is used

- added some template vars of the frontend to be also accessible in backend (e.g.: $page_alias)

- added param "allow_none" to all content block types to specify if the predefined default value will be used if no value is entered

- fixed bug where empty values where never be stored

- fixed bug where default value in frontend was ignored if the "allow_none" param was changed after an empty value has been stored

- added param "sortable_items" to create a sortable multiple select list (select list will result in a table with checkboxes; only order of selected items will be stored and showed at the top of the list; unselected items will be appended in that order they are placed in the template)

-fixed a bug where the option searchable was not saved