re-added MultiScript

The very first Godot version (when it was open sourced) had "MultiScript" which lets you use multiple scripts on one object.
With the addition of mulitple new scripting languages (VisualScript, soon C# and GDNative) it can be of use to combine scripts rather than delegating (with huge maintainance cost) or creating child nodes
which could impact performance.

I used the code from 0b806ee as the base and made it work with the current master.

modules/multiscript/config.py

@@ -0,0 +1,8 @@
+
+
+def can_build(platform):
+    return True
+
+
+def configure(env):
+    pass