Moneropedia localization

Created by: el00ruobuob

We have long waited for this, so i've decided it was about time to do it. Moneropedia, localized, finaly This solves #700 (closed)

I have briefly test it on english and polish. I had to update a lot of polish file to make it work correctly.

It's basically working by defining a moneropedia collection per language, and require the use of a tag on every page for the ruby script to know which language it is. This tag is self-removed by the ruby script.

Also, each moneropedia entry in _i18n folder must have a part of the front matter (the one handled by the script) but it is interprated as md code, not as front matter. So the script has to remove it. Please check that it does not add glitches elsewhere.

The _i18n front matter of localized files should include the english terms, so any new entry in moneropedia is working de-facto when untranslated.

We also have to document everything in the readme. I could do it later this week-end, or next week.

And of course, enjoy!

Up to the team to work @erciccione!