Configuration Editor for machines and targets (Overhaul)

Summary

Same functionality as #335. Did a partial rewrite and fixed some problems that existed in that pull request

refactoring of the code (still WIP)
changed the storage layout to simplify crud commands
renamed some things from "... Config" to "... Tech Data Set"
fixed: a user always needed to refresh the page to see the changes they made
tree view in the editor remembers which elements were collapsed/expanded
the editor sider remembers its size and if it was collapsed or not
fixed: renaming of elements works now
changed the layout:
- the buttons above the treeview have more spacing
- Removed the wrapper around machine configs
- the sider and header in the editor are fixed => scrolling only affects the shown content if it is too large