Move main executable source to its own directory (#248)

* Move main executable files to their own directory

* Adapt the build to the new file structure

... and fix some weird #include's that were relying on the project root
being an include directory.

Ja2/ja2.h

@@ -0,0 +1,8 @@
+#ifndef __JA2_H
+#define __JA2_H
+
+#define	JA2VERSION_NUM				0.01				
+#define JA2MAPVERSION_NUM			1.00
+
+#endif
+