Store the current IME's token in the system bar for changing the current IME...

Store the current IME's token in the system bar for changing the current IME to a shortcut IME from the system bar

Bug: 3212206
Bug: 3201828

- Added a shortcut IME button. This will be used for calling a shortcut IME (e.g. Voice input)
- Made the positions of IME buttons left aligned
- IME token is required to change IME because of the security reasons.

Change-Id: I48ba5e2509b3aa1bfd2394f9201427fa6b93c6d3