Setup: Exclude all tests data from release package

Fixes #3205.
Setup: Include all tests data in release package

It seems I initially misunderstood what people wanted.

Fixes #3205.
Cleanup: Move all the imports to the top
Cleanup: Include the formats declaration inside main()
Remove usage of third party itools library

This implies removing the --engine option in odf2xliff.
Cleanup: Remove unnecessary function