CMake: Packaging: No default package contact
core/CMakeLists: Add subdir header files
Merge pull request #255 from lclc/develop

CMake: Packaging: No default package contact
CMake: remove unused hack for ZMQ

The ZMQ submodule is used for Windows that does not have proper
package management. But the hack is not used for Windows and
therefore unnecessary.
Merge pull request #260 from toxeus/removeZMQhack

CMake: remove unused hack for ZMQ
Merge pull request #261 from lclc/swifg

core/CMakeLists: Add subdir header files