Warning : big linking changes here!

Remove legacy way to link core/database/gui DK libraries with dng internal components.
Use CMake OBJECT definition as all other places and reduce the puzzle complexity.

Note: This wrap around implemented by Veaceslav Munteanu was necessary 2 years ago
to link properly with Exiv2 0.26 beta with private XMP SDK used internaly.
XMP SDK exists too in digiKam core and we obtain multiple linking objects at end.
Sound like this problem is finaly fixed in Exiv2 now.

Export ballowrap component as Cmake OBJECT to be homogeneous

And finaly the most important step: export the digikamcoreConfig cmake script for external contribution.

TODO: export digikamdatabaseConfig and digikamguiConfig Cmake scripts.

check if compilation workflow is not broken under MacOS and Windows.
check if compilation workflow is not broken with all possible Cmake configuration options.

CCMAIL: metzpinguin@gmail.com