Translatable tutorial again

Useful for allowing non-english speaking Virtaal users to quickly learn how to use it.

Also includes new entries in the tutorial for topics not covered before, like terminology or accelerators.

Tested in local and works fine, but further testing might be a good idea.

It is a first step for closing http://bugs.locamotion.org/show_bug.cgi?id=1421

Supersedes PR #6