Migration request from IBusConfig to GSettings

Summary:
kimpanel-ibus-panel uses IBusConfig and I'd ask to migrate it to GSettings and delete IBusConfig.

https://groups.google.com/forum/#!topic/ibus-devel/Mu1IoFX-bKE

Test Plan: Run ibus-setup and changes "Next input method" or IMEs and KIM panel works fine.

Reviewers: #plasma, hein, xuetianweng

Reviewed By: xuetianweng

Subscribers: davidedmundson, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D11061