Remove translations imported from skeleton module.

They has different messages, and it's easier for translators to start
from the clean pot than update different translation.
Add meaningful module descritption to the module.desktop.in

Also drop useless translations imported from the skeleton module.
Move Productivity from "Advanced" category to "Extensions"
Use standard E function to check config version compatibility.

The open coded version of the check was incorrect anyway.
Make some more messages translatable
Make gettext actually work for the module.

I had no will to dig into autofoo stuff, so i just copied over working
code from some other module.
Add russian translation.
Use D_ for dgettext() to better follow coding conventions.
Simplify .gitignore a bit