Extended and Improved XML-RPC API

1) Added metaWeblog.getPost method
2) Added mt_getPostCategories method
3) Added metaWeblog.deletePost method alias for blogger.deletePost
4) Improved xmlrpc_getCategoryList method to support both MetaWeblog & Movable Type APIs.
Further Improved Categorize XML-RPC Support

Fixed couple of bugs.
Now Categorize Module offers full support for both MovableType and MetaWeblog APIs.
Merge branch 'feature/xmlrpc' into develop