Remove .deb packaging, not done with CMake.

CMakeLists.txt

@@ -17,19 +17,12 @@ core_find_git_rev(RELEASE_IDENTIFIER)
 string(TIMESTAMP PACKAGE_TIMESTAMP "%Y%m%d.%H%M" UTC)
 set(CPACK_PACKAGE_VERSION ${PROJECT_VERSION}~git${PACKAGE_TIMESTAMP}-${RELEASE_IDENTIFIER}-${DISTRO_CODENAME})
 
-set(CPACK_PACKAGE_DESCRIPTION_SUMMARY "Xournal++: Notetaking software designed around a tablet")
-set(CPACK_GENERATOR "DEB"  CACHE STRING "Alternativelly generate RPM. Needs rpmbuild.")
-set(CPACK_DEBIAN_PACKAGE_MAINTAINER "Xournal++ Team")
-set(CPACK_DEBIAN_PACKAGE_CONTROL_EXTRA "${CMAKE_CURRENT_BINARY_DIR}/cmake/postinst")
-
 configure_file (
     cmake/postinst.in
     cmake/postinst
     @ONLY
 )
 
-include(CPack)
-
 include (FindPkgConfig)
 
 set (PACKAGE_DATA_DIR "${CMAKE_INSTALL_PREFIX}/share")