Harmattan: Fix cmake and packaging files

* Use correct CMAKE_INSTALL_PREFIX, so setting CMAKE_INSTALL_RPATH is not needed
* Use correct GNU Make DESTDIR, so absolute paths in cmake install commands are not needed
* Use only one install command for target Plugins (now it is possible because paths are correct)
* Move share files from opt area in debian/rules, so absolute paths in cmake are not needed

REVIEW: 112832