Accept "on" value for remember me checkbox input value

Accept a value of "on" for login screen's "remember me" input value.
This is what gets sent as default by the browser when an
<input type="checkbox"> is checked.

Previously only "1" was accepted which meant checkboxes would need to
explicitly specify a value="1" in their definition.

Fixes #96
Merge pull request #97 from nurpax/remember

Accept "on" value for remember me checkbox input value