Compatibility OGRE 1.10/Removed unnecessary deps

Changed StringUtil::BLANK to an empty string, added ifdefs for Xalafu
compatibility and added some include files for classes that were only
forward declared but never included. (Wouldn't compile on VS2013)

So here are all the changes needed to make this compatible with VS 2013 and the latest OGRE from the repo.
Not sure what the if here is for...