Removes _DEBUG directives from all source files

This commit removes the #ifdef _DEBUG statements at the top of all source code files per issue #482. It also updates the doc files to stress that the speedup observed for hydraulic analysis with the MMD node re-ordering method only applies to single period runs.

src/project.c

@@ -7,17 +7,11 @@
  Authors:      see AUTHORS
  Copyright:    see AUTHORS
  License:      see LICENSE
- Last Updated: 04/20/2019
+ Last Updated: 05/15/2019
  ******************************************************************************
 */
 
-#ifdef _DEBUG
-  #define _CRTDBG_MAP_ALLOC
-  #include <stdlib.h>
-  #include <crtdbg.h>
-#else
-  #include <stdlib.h>
-#endif
+#include <stdlib.h>
 #include <stdio.h>
 #include <string.h>