Fixed one typo in response_helpers which caused is_admin context variable not to work correctly. Created new checkLinkNameForId function that checks if link_name is correct when creating new user and modifying existing one. This is now used for validation instead of doesLinkNameBelongToId in UserForm clean_link_name function. The previous validation function didn't allow to create new users and modify linkname of existing ones. Additionally I created new doesLinkNameExist helper function.

This is an optional add-on app, flatpages.

For full documentation, see either of these:

    * The file docs/flatpages.txt in the Django distribution
    * http://www.djangoproject.com/documentation/flatpages/ on the Web

Both have identical content.