Adding the option to show the keys of translations

[ThoWagen]

Sometimes it is helpful to show the keys of translations on the website directly in development systems. This can help non-technical staff members to customize the translations.

So in this PR a option for this is added. The translatable text has the format "*<key>*" to indicate that it is translatable.

[demiankatz]

Thanks, @ThoWagen! This is a good idea, though I may not have time to review it in depth before I get back from vacation in a couple of weeks (though I will try if time permits). I'd welcome input from others in the meantime!

[demiankatz]

Thanks again, @ThoWagen -- I did find a little time to look more closely at this, and I've left a few thoughts (many of them pretty repetitive. :-) ).

[demiankatz]

Thanks again, @ThoWagen -- one last thought before I do hands-on testing. :-)

[demiankatz]

Thanks, @ThoWagen -- I did a little bit of hands-on testing and found a couple of small remaining issues. See below. I also merged this with the latest dev branch to be sure I was testing the latest code, so you'll want to pull down my changes before making more of your own.

[demiankatz]

One other thought: maybe this would be even more clear if the "language code" for this was "debug" rather than "keys".

[ThoWagen]

I renamed it to "debug". I think you are right. It is not really obvious what "keys" means on first glance.

[demiankatz]

Thanks, @ThoWagen -- some fairly trivial comments. I'm out of time for today but hope to get this merged tomorrow. If you're busy and would like me to make the suggested changes myself, I am happy to help when I have time to do more hands-on testing tomorrow... just passing them along to you in case you're able to get there first.

[demiankatz]

I've merged the latest dev branch into this and made a very small whitespace adjustment to config.ini; I think this is ready to merge now. Thanks again, @ThoWagen!