#95 Support creating pot file without line numbers

[Mojca Miklavec]

When recreating pot files the diffs are always huge just due to constantly changing line numbers.
Translators don't use the source code for translations and are only testing with the actual software, so the added value of line numbers is exactly zero. I remove the line numbers during conversion to po files, but it would be so much nicer if they could already be excluded in the pot file.