Ctest configuration

This replicates issue #115 (closed) , which in turn traces back to !103 (merged), regarding ctest and gtest.

I finally left the project as this (checkout branch frame-base-tests):

• wolf/src/tests --> here all the gtest files are located

• In wolf/CMakeLists.txt

if(BUILD_TESTS)
    enable_testing()
endif()

• In wolf/src/CMakeLists.txt

if(BUILD_TESTS)    
    MESSAGE("Building tests.")
    add_subdirectory(test)
endif()

src/CMakeLists.txt

@@ -481,12 +481,6 @@ INSTALL(DIRECTORY ${SPDLOG_INCLUDE_DIRS} DESTINATION "include/iri-algorithms/")
 
 export(PACKAGE ${PROJECT_NAME})
 
-IF(BUILD_EXAMPLES)
-  #Build examples & tests
-  MESSAGE("Building examples.")
-  ADD_SUBDIRECTORY(examples)
-ENDIF(BUILD_EXAMPLES)
-
 #############
 ## Testing ##
 #############
@@ -498,3 +492,9 @@ if(BUILD_TESTS)
 
 endif()
 
+IF(BUILD_EXAMPLES)
+  #Build examples & tests
+  MESSAGE("Building examples.")
+  ADD_SUBDIRECTORY(examples)
+ENDIF(BUILD_EXAMPLES)
+