LayoutLib: updated fake accessbility manager and ensure there's an InputMethodManager

We had replaced the accessibility Manager but it lacked some new API. Obvisouly
this is fragile and should be fixed, but this works for now.

After fixing this there was another issue with the lack of InputMethodManager.
To fix this I had to create an implementation of IInputMethodManager which
normally comes from a binder object.

I may want to do a similar trick with the accessibility manager later.

Change-Id: I28c6494e333f39072f348d0199124efac93256a5