Removed getParagraphElement from OdtDocument

This function only redirected to the OdfUtils version and many callers
already had an existing instance of OdfUtils to use. Any callers who did
not have an instance of OdfUtils now create one to continue using the
function.
Remove style element functions from OdtDocument

Removed getStyleElement, getParagraphStyleElement and
getParagraphStyleAttributes from OdtDocument as these functions simply
redirect to their implementations in odf.Formatting.
Merge pull request #777 from satsuper/interface-cleanup

OdtDocument interface cleanup