Core/Battleground: Some (minor) code optimizations

- All access to Battleground vars are done using funtions (Remove friendship from Battleground and BattlegroundMgr)
- Move specific 47 mins arena check to battleground code as its generic to all arenas
- Create PreUpdateImpl and PostUpdateImpl functions. Specific battlegrounds will implement those if needed (No more need of call Battleground::Update inside specific BGs)
- Modify Create function to use only one parameter
- Remove EventPlayerCapturedFlag from Battleground class, only one BG implements it and it's not used outside that BG.

src/server/game/Maps/MapManager.h

@@ -33,8 +33,6 @@ struct TransportCreatureProto;
 class MapManager
 {
     friend class ACE_Singleton<MapManager, ACE_Thread_Mutex>;
-    typedef UNORDERED_MAP<uint32, Map*> MapMapType;
-    typedef std::vector<bool> InstanceIds;
 
     public:
 
@@ -151,11 +149,14 @@ class MapManager
         MapUpdater * GetMapUpdater() { return &m_updater; }
 
     private:
+        typedef UNORDERED_MAP<uint32, Map*> MapMapType;
+        typedef std::vector<bool> InstanceIds;
+
         // debugging code, should be deleted some day
         void checkAndCorrectGridStatesArray();              // just for debugging to find some memory overwrites
         GridState* i_GridStates[MAX_GRID_STATE];            // shadow entries to the global array in Map.cpp
         int i_GridStateErrorCount;
-    private:
+
         MapManager();
         ~MapManager();