universal access : Linking "Enable by Keyboard" to Universal Access Panel

The issue was that toggling the "Enable by keyboard" switch did not alter the state of the Typing Assist section. It was staying as "Off" even when "Enable by keyboard" was on.

The reason was because the update_accessx_label was checking the other 3 options(Bounce keys, Slow keys and Sticky keys) but not the keyboard toggle. So I added keyboard toggle in the condition which checks whether to update the label.

Fixes #495 (closed)