Implement interaction with IBus

- add default handler for ibus events that works with WinForms TextBox
- implement registering a control so that we can forward some events
  to ibus
- forward some events of the control to ibus
- translate key events into the form ibus expects
- hook up WSKeyboardControl with keyboard controller

Change-Id: I4d7f9edd889b747cd61764eb68489391aa64d0ee
Merge "Implement interaction with IBus" into fw/KeyboardingV2