build: CMake refactoring

Includes:
- refactor build_lib and build_lib_example macros
    - unify src and contrib macros
    - replace macro with function not to leak definitions
    - parse list of arguments
- different cmake-format file for modules to list one item per line

examples/realtime/CMakeLists.txt

@@ -1,9 +1,10 @@
 if(${ENABLE_REALTIME})
-  set(name realtime-udp-echo)
-  set(source_files ${name}.cc)
-  set(header_files)
-  set(libraries_to_link ${libcsma} ${libinternet} ${libapplications})
   build_example(
-    "${name}" "${source_files}" "${header_files}" "${libraries_to_link}"
+    NAME realtime-udp-echo
+    SOURCE_FILES realtime-udp-echo.cc
+    LIBRARIES_TO_LINK
+      ${libcsma}
+      ${libinternet}
+      ${libapplications}
   )
 endif()