Fixed execution workflow and some minor stuff

This is (IMHO) a major improvement. I
 - fixed the execution workflow, so that the selected suggestion gets executed, after being passed the parameter of it's input fields.
 - improved payment page generator to properly work with statements and to use more direct SQL for performance reasons
 - started localizing the strings and added a (first draft) German translation

@pdelbar: Please check if your stuff still works and merge asap - this is going to be a pain otherwise