editor tutorial: added support for common triggers
added a rename dialog for new topologies
added a link
added new empty "data access" tutorial
moved editor to page center
added topology export functionality
fixed bad characters in exported topologies filename
moved export functionality to external file; created import function (which can detect the file, but not understand it)
re-enabled topology import buttons in topology list
topology importer can now restore devices
changed MIME type of export file
finished topology import: importer can now completely restore the topology as given by the file
Merge branch 'master' into working_editor
fixed alert texts for deleting a topology from the editor
fixed missing import of connection[attrs]