Remove redundant Protobuf3 dependencies

The following lines are in many of the CMakeLists.txt files:

find_package(Protobuf3 REQUIRED)
target_link_libraries(cta-taped ctatapedaemon ctacommon ${PROTOBUF3_LIBRARIES})
set_property (TARGET cta-taped APPEND PROPERTY INSTALL_RPATH ${PROTOBUF3_RPATH})

The only places we use protocol buffers are:

• In the communication with CTA Frontend
• In the internals of the objectstore

This dependency should not exist outside those two use cases and should be removed everywhere else.