ENH: Refactor find_* command framework/appbundle search order impl.

- CMAKE_FIND_FRAMEWORK and CMAKE_FIND_APPBUNDLE are supposed to specify
    whether to find frameworks/appbundles FIRST, LAST, ONLY, or NEVER.
  - Previously this affected only the placement of CMAKE_FRAMEWORK_PATH
    and CMAKE_APPBUNDLE_PATH with respect to the other path specifiers.
  - Now it behaves as documented.  The entire search path is inspected for
    each kind of program, library, or header before trying the next kind.
  - Additionally the ONLY mode is now honored for headers so that users
    do not end up with a library in framework and a header from elsewhere.

Source/cmFindLibraryCommand.h

@@ -68,7 +68,10 @@ public:
 protected:
   void AddArchitecturePaths(const char* suffix);
   void AddLib64Paths();
-  std::string FindLibrary(const char* name);
+  std::string FindLibrary();
+private:
+  std::string FindNormalLibrary();
+  std::string FindFrameworkLibrary();
 };