Add API for cache loading, deleting and saving to the cmake class.

Migrate existing users of the CacheManager API to use the new
API.  The CacheManager will be going away soon.

Source/CursesDialog/cmCursesMainForm.cxx

@@ -639,7 +639,7 @@ int cmCursesMainForm::Configure(int noconfigure)
 
   // always save the current gui values to disk
   this->FillCacheManagerFromUI();
-  this->CMakeInstance->GetCacheManager()->SaveCache(
+  this->CMakeInstance->SaveCache(
     this->CMakeInstance->GetHomeOutputDirectory());
   this->LoadCache(0);