Support external builds of python bindings, gui, ctbgui and moench stuff (#440)

Use already installed version of the slsDetectorPackage. Assumes that the library has already been built and installed either on a system wide location or pointed to by CMAKE_PREFIX_PATH

slsDetectorCalibration/moenchExecutables/CMakeLists.txt

@@ -56,7 +56,8 @@ foreach(exe ${MOENCH_EXECUTABLES})
         ../dataStructures 
         ../interpolations
         ../../slsReceiverSoftware/include/
-	../../slsSupportLib/include/
+	    ../../slsSupportLib/include/
+        ${SLS_INTERNAL_RAPIDJSON_DIR}
     )
 
     target_link_libraries(${exe}