Add Korean Translation

[wbnns]

인사와 환영! The Korean translation is being reviewed and is nearly complete. Greetings to approximately 75 million Koreans that can now learn more about Bitcoin in their native language.

Thank you very much to all of the translators, reviewers and coordinators that have assisted us with this!

Here's a link to the live preview:
http://bitcoinko.us.to/ko/

[saivann]

@gwb3 Thanks! Can you add or page.lang == 'ko' on _layouts/base.html, line 11 ? This should apply the sans.less stylesheet to all Korean page. This allows to use the default "Sans" font when dealing with characters poorly (or not) supported by the Ubuntu font.

Similarly, we'll have to apply the rtl.less (right-to-left) stylesheet for right to left languages like Hebrew when adding them. You don't need to do it for Arabic since we already have outdated translations published, so it's already done in this case.

[wbnns]

@saivann Done, sir!

[saivann]

@gwb3 Thank you for all your great work on this!! This finally LGTM. I've found two or three broken links with the remaining url check, I'm going to fix them right after I merge this.