BGE Clean-up: New EXP prefix for the BGE Expression module

The expression module now uses an EXP prefix and it follows a
distribution similar to blender.

Additionally the hash function in EXP_HashedPtr.h was simplified and the
files EXP_C-Api.h &.EXP_C-Api.cpp were deleted because were unused.

Reviewers: campbellbarton, moguri, sybren, hg1

Projects: #game_engine

Differential Revision: https://developer.blender.org/D1221

source/gameengine/GameLogic/SCA_KeyboardManager.cpp

@@ -33,10 +33,10 @@
  */
 
 
-#include "BoolValue.h"
+#include "EXP_BoolValue.h"
 #include "SCA_KeyboardManager.h"
 #include "SCA_KeyboardSensor.h"
-#include "IntValue.h"
+#include "EXP_IntValue.h"
 #include <vector>
 
 SCA_KeyboardManager::SCA_KeyboardManager(SCA_LogicManager* logicmgr,