Move preference page to new UI plugin.
This is piece six of change https://git.eclipse.org/r/c/159828 being split into pieces.
Splitting is done for code reviewing reasons.
Change-Id: I9db0f3053ef9524a5b79a0fc9b8198ff241acb1a
Signed-off-by: Martin Weber <fifteenknots505@gmail.com>