Core/Scripts: Split script subdirectories into independent modules

* Makes it possible to define the linkage for every module
* Move the ScriptPCH into the root directory
* Changes the SCRIPTS cmake variable to a string type:
  -> -DSCRIPTS=0 is -DSCRIPTS="minimal-static" now
     (builds commands and spells statically)
  -> -DSCRIPTS=1 is -DSCRIPTS="static" now
     (builds all modules statically)
  -> -DSCRIPTS="dynamic"
     (builds all modules dynamically)
  -> Also the default value which is provided by the SCRIPTS
     variable is overwriteable through the SCRIPTS_COMMANDS,
     SCRIPTS_SPELLS... variable.

src/server/scripts/ScriptPCH.cpp

@@ -0,0 +1,6 @@
+/* Copyright (C) 2006 - 2009 ScriptDev2 <https://scriptdev2.svn.sourceforge.net/>
+* This program is free software licensed under GPL version 2
+* Please see the included DOCS/LICENSE.TXT for more information */
+
+#include "ScriptPCH.h"
+