Improve appearance of kimpanel candidates popup
- Use PlasmaComponents3 where possible.
- Disable mouse hover highlight because mouse clicks do not seem to work anyway.
- Use hover highlight for selection instead to improve readability. This also helps it look more in line with the new Breeze.
- Replace the input method list checkbox in settings saying just "Vertical" with RadioButtons for "Vertical" and "Horizontal".
- Few fixes for spacings so that characters don't touch each other and make it unusable.