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/constraint_fix.h

@@ -11,6 +11,8 @@ namespace wolf {
 
 class ConstraintFix: public ConstraintSparse<3,2,1>
 {
+    public:
+        typedef std::shared_ptr<ConstraintFix> Ptr;
     public:
 //        static const unsigned int N_BLOCKS = 2;