Resolve "Enable Standard Point Positioning (SPP) computation"

Closes #2 (closed)

cmake_modules/FindRTKLIB.cmake

-#edit the following line to add the librarie's header files
-
-FIND_PATH(RTKLIB_INCLUDE_DIR rtklib.h /usr/include /usr/local/include ~/RTKLIB/src)
-GET_FILENAME_COMPONENT(RTK_LIB_PATH ${RTKLIB_INCLUDE_DIR} DIRECTORY)
-
-IF (RTKLIB_INCLUDE_DIR)
-   SET(RTKLIB_FOUND TRUE)
-ENDIF (RTKLIB_INCLUDE_DIR)
-
-IF (RTKLIB_FOUND)
-  IF (NOT RTKLIB_FOUND_QUIETLY)
-    MESSAGE(STATUS "Found RTKLIB: ${RTKLIB_INCLUDE_DIR}")
-  ENDIF (NOT RTKLIB_FOUND_QUIETLY)
-ELSE (RTKLIB_FOUND)
-  IF (RTKLIB_FIND_REQUIRED)
-    MESSAGE(FATAL_ERROR "Could not find RTKLIB")
-  ENDIF (RTKLIB_FIND_REQUIRED)
-ENDIF (RTKLIB_FOUND)