Controls enabling and disabling of IME input composition.

Some languages use complex input methods which involve opening windows to insert characters. Typically, this is not desirable while playing a game, as games may just interpret key strokes as game input, not as text. By default, Unity will enable IME composition when in text fields, and disable it otherwise. However, when you want to implement your own input GUI, you may want to have control over this yourself, which is possible using the imeCompositionMode property. Set it to Auto for the default behavior, or On or Off to explicitly enable or disable IME composition.