Fixed Content is not allowed in prolog errors

Before this fix, it was always tried to parse LiteralData as XMLObject.
This caused the above exception (in the log it is declared as "Fatal
error"). All tests run through, is there a situation thinkable, where
the parsing is actually needed? Literal XML values maybe?
Merge branch 'outputdataitem-refactor'
Merge pull request #14 from bpross-52n/master

Fixed "Content is not allowed in prolog" errors.