Changes to allow source packaging via CPack

- Refactored all packaging related stuff into a single CMake module
- Build should no longer fail when optional sources (e.g. broctl)
  do not exist in the source directory, instead a warning is issued
- Additional configure options to change packaging behavior

cmake/CheckOptionalBuildSources.cmake

@@ -0,0 +1,21 @@
+# A macro that checks whether optional sources exist and if they do, they
+# are added to the build/install process, else a warning is issued
+#
+#         _dir: the subdir of the current source dir in which the optional
+#               sources are located
+# _packageName: a string that identifies the package
+#     _varName: name of the variable indicating whether package is scheduled
+#               to be installed
+
+macro(CheckOptionalBuildSources _dir _packageName _varName)
+    if (${_varName})
+        if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${_dir}/CMakeLists.txt)
+            add_subdirectory(${_dir})
+        else ()
+            message(WARNING "${_packageName} source code does not exist in "
+                            "${CMAKE_CURRENT_SOURCE_DIR}/${_dir} "
+                            "so it will not be built or installed")
+            set(${_varName} false)
+        endif ()
+    endif ()
+endmacro(CheckOptionalBuildSources)