Help: Move Qt tool invocation information to a generic cmake-qt manual.

Add an introduction about the use of different package types, and the
ability to use Qt 4 and 5 versions together in a single buildsystem.

Add a section about automatic linking of the qtmain.lib library and
how to disable it.
Help: Note that AUTOMOC consumes the defines and includes from targets.
Help: Add information about INTERFACE_AUTOUIC_OPTIONS.
Merge topic 'cmake-qt-manual' into next

4271a4ed Help: Add information about INTERFACE_AUTOUIC_OPTIONS.
7935f4de Help: Note that AUTOMOC consumes the defines and includes from targets.
2739a6f9 Help: Move Qt tool invocation information to a generic cmake-qt manual.