Implement Saving and Loading

[Rob4001]

Currently the system creates a temporary folder and creates a copy of the default.tingapp inside it: it would be nice to:

• [x] Save TingApp to a proper folder
• [x] Load TingApp from folder
• [x] Save contents of file on ctrl-S, menu save or upload/run press
• [x] Import files into tingapp with drag+drop or menu load

[joerick]

Complete