Support for DirectDebits

Hey,

I needed to do DirectDebits and your work was the only one that did already some basics. After I finished I had nearly rewritten all your wok and changed the pattern to build the XML.

I don't want to maintain a second library and think it should be brought together to build one SEPA library for PHP to out the affords together.

Please, take a look and tell me what you Think about it.

regards Sören

P.s. I just realized a lot of typos, before a merge I will cleanup the git history :-)