Task-number: QTCREATORBUG-2753

Reviewed-by: hjk

Task-number: QTCREATORBUG-3378

Task-number: QTCREATORBUG-3380

 * Fix all warnings about non-explicit constructors except for those
   in 3rdparty code.

For later use in IFindFilter.

Reviewed-by: ck

Reviewed-by: ck

Make the check more generic, to also work for all other Qt namespaces
than qt.ver.s.ion. Still there's something broken in Qt webkit or so.

Reviewed-by: ck

Fixes the broken topic chooser and keyword resolving.

Reviewed-by: ck

Reviewed-by: kh

Both implementations are now split into two source files, based on the
base class type. They share also a commen implementation, but the class
interface looks now clean to the outside. Adopt other classes for use.