libconnman-qt.pro: allow parallel installation for Qt4/X11 + Qt4/Embedded

New default target is connman-qt$$QT_MAJOR_VERSION. This implies a
new default include path for Qt4 of $$PREFIX/include/connman-qt4
instead of $$PREFIX/include/connman-qt. Users of pkg-config are not
affected by this change.

Passing TARGET_SUFFIX=qt4e to qmake changes the target to connman-qt4e.

Also convert the counters example to use pkgconfig and version-agnostic
include directives.

Signed-off-by: Andreas Oberritter <obi@opendreambox.org>
libconnman-qt.pro: streamline pkgconfig generation

Let qmake handle the generation of connman-qt*.pc. This also fixes
issue #82 (connman-qt4.pc is installed in lib folder).

Signed-off-by: Andreas Oberritter <obi@opendreambox.org>