Increased usability

- enhanced user interface, especially on explorer page
- added icons and tooltips to modify the diagram on page 1
- better page transitions and hash support when changing pages
- added initial page loading indicator
- fixed undo/redo for list attributes (page 2)
- added result table for page 2 (incl. raw data export from rails backend)
- fixed several drag drop issues
- fixed issue where changes to the graph on page one were not persistent
- removed old labels of axes