Merge pull request #1 from rmatil/feature/generate-Subnav

Add posiblity to genereate a submenu automatically
Adds debug modus in settings
Bugfix in preselecting checkboxes
Adds category support for pages
Removes unnecessary comment
Adds rudimental support for categories
Big refactoring...
Big refactoring... Adding new files
Adds BackendAccessInterface and class BackendAccess to access the database
Adds BakendAccessInterface
Adds class thumbnail generator
Database entry will be inserted even if creation of the thumbnail failed
changes language in comments
Removes protocol of http_root constatn
Adds header 401
Adds info box
Adds png thumbnail generator
Adds png support for thumbnail creating
Changes header(location:...) to HTTP_ROOT
Updates logout link