By default now, fields have a transparent border if not focused and
accent-color border if focused.
Set `bordered: false` for no border at all.
The register and forgot buttons on the SignIn screen are now disabled,
since their functions aren't implemented yet.
http://es6-features.org/#PropertyShorthand
Instead of doing {"foo": foo, "bar": bar, ...}, we can just do
{foo, bar} now.
The function parameters of EventHandlers have all been renamed to
camelCase to make use of this, as the JS style conventions intend.
Other functions will follow in a later commit.