Rotate IMEs (subtypes) by Meta+Space.

With this CL, PhoneWindowManager starts monitoring Meta+Space to trigger
input method rotation.

Note that InputMethodManagerService currently supports only one way
rotation.  Currently there is no difference in the behavior between
Meta+Space and Shift+Meta+Space.  Reverse rotation will be supported in
a subsequent CL.

Bug: 25753404
Change-Id: I4005692215edfcf8bed3e86b1e07000148f986f5