Convert English docs to markdown

- Issue #1180: All English docs are written in markdown now.
  HTML is only used when it is required for theming or for elements that have no markdown counterpart.

- Fix a bug where pagination is not shown
  The pagination used the "||" operator that does not exist in Liquid, "or" does.

- Markdown parser set to Redcarpet
  The default Markdown parser Maruku is not able to build the documentation and throws an error.
Merge pull request #1276 from jgillich/gh-pages-1

Converted Docs from HTML to Markdown
Added in 'translations' docs

This still needs docs on how to translate the Ghost platform.
Include 'example_translation' folder
Correct Chinese language code, cross-link language versions

As discussed in #1233 and #1344
- added {{page.section}} metadata so as to be able to reference URI components (site_url, page.lang, page.chapter, page.section) individually
- refactored canonical meta tag in default layout to refer to the same page with trailing slash: site_url/[page.lang/][page.chapter/][page.section/]
- added alternate-hreflang meta tags in default layout to help search engines understand about different language versions
- added visible cross-language links in top navbar with .navbar-right styling for each page, using the URI components mentioned above to construct the different language links (essentially but not quite the same logic as for alternate-hreflang meta tags)
- included Bootstrap v3's .navbar-right styles in main.css, seeing as they seem to be missing from bootstrap.css at the moment and I don't want to mess with it. :D

It may be appropriate to edit README.md or add a CONTRIBUTING or TRANSLATING file to explain how to get started with new translations, and/or move translations to a more formal mechanism...
Merge pull request #1344 from DuncanMacWeb/gh-pages-interlink-translations
Merge pull request #1422 from matthojo/gh-pages

Documentation on how to translate the docs
Removed unused files

This includes the dummy 'es' translation and some old 'cn' files.
Convert `zh` to Markdown
Updated the example_translation to match updates
Merge pull request #1425 from matthojo/gh-pages2

Convert translations to Markdown