eCAL 5.5.5

Changelog

eCAL v5.5.5:
* documenation:
  * CMake options documentation improved
  * Npcap section installation and usage added
  * instruction how to build the documenation added
* common:
  * CMakeLists.txt files moved outside source folders
* thirdparty:
  * protobuf updated to 3.11.4
  * asio updated to 1.14.0
* core:
  * MacOS port prepared
* language bindings
  * CSharp JSONProtobufSubscriber added
  * CSharp protobuf publisher / subscriber API added
* apps
  * monitor application renamed from mon to mon_gui