Extensive reworking of client-side error display.

[scriptbae]

Integrates error reporting into the API. Both layers of the server software now support an error reporting pipeline with broadly homogeneous coverage.

Integrates error reporting into the client-side JS and HTML by forwarding human-readable errors reported by the server, to the client. These error reports are implemented as a submit button animation. The submit button momentarily becomes red, and displays the error text.

Conclusively resolves #50 and #57.

The fix for #57 was identified as elevated priority non-critical by @inspectorG4dget.

The fix for #50 includes extensive coverage and a functional and visually appealing for edge cases which may be included at the EECS Council demo.

Conclusively resolves #20.

The dbhandler module now uses toml instead of ConfigParser, which exposes a more Pythonic, json-like API. Unlike JSON, TOML provides a simplified writing style, allowing for configuration composition to be less time-consuming.

The toml module is actively maintained by Will Pearson, a uOttawa student.

Partially resolves #43. Some of the functions in backend.py now have Pydoc docstrings. This will be actively improved upon in the immediate future alongside test development.

[scriptbae]

Pending additional, unmentioned UI development requirements, I'm also signing off on, and recommending, closing ui-devel for the time being. Immediate upcoming development will concern documentation and automated testing.