bug fixed: when editing entry in admin list an error was shown that public index is missing | and done a lot of stuff for pages_cost

- streamlined index_check_field (was very unstructured)
- bug fix: status.php a missing $ sign for variable added
- splitted config into local and general
- beginning of cost implementation

updated DB scheme, changed login handling (now users in users.txt), new superadmin page, adjusted config, added number of registrations in overview