Add file tests, clean up and simplify

- Test html, idml, dtd, odg/p/s/t File type upload
- Use ZanataRestCaller rather than manually creating projects, versions
- Remove unused imports
- Add a null pointer check on opening files
It is duplicated. Just as I suspected!

![Aha!](http://www.televisioned.net/62511/startrektng-62511.gif)