Sneak preview of the new Hyrise frontend

This commit contains the latest work on the HYRISE frontend, including

- new hyrise icon and favicon for the page
- new "flat design" for the hyrise visualizer
- it is now possible to load and explore tables
- query plans can now be viewed in detail and edited using either the plan visualizer or a json editor
- query execution information is displayed on page two
- added editors for plan op attributes, incl. complex editors for functions and predicates (incl. generic approach for any complex types)
- added javascript editor as preparation for custom javascript operators
- clean up queries generated by the data explorer to only include legal edges and operations (strip "input" parameter, remove double edges, etc)
- added undo/redo stack for plan visualizer (not yet fully supported, wip)