PackageManager: set LANG env for pkginfo helper. Refs #2694

- Rely on YUM Python library for comps localization.
PackageManager: use vanilla CompositeController. Refs #2694
PackageManger: show categories as radio buttons. Refs #2694
PackageManager: keep groups selection on Back button click. Refs #2694

- Highlight installed/removed groups by CSS class
PackageManager: added "Everything" default category. Refs #2694
PackageManager: improved limit case handling. Refs #2694
Updated online manual. Refs #2694
PackageManager/Tracker: added setNextPath() for class reusability. Refs #2694