This refactors the data handlers into a more standard/understood model-like architecture, to prepare for a new, more robust config system.
It also fixes a problem with creating new Notes and uploading new Photos via the web interface (related to #58).
Finally, it speeds up docker builds by sending in less files, which aren't necessary or will be built anyway.
This is all in preparation to allow building #13 more robustly.
Additionally:
- Make expense and budget modal "reset" once closed, saved, or deleted.
- Make manifest icons dark
- Budgets in small screens should be full-screen
- Minor code cleanup
Fixes#48
