Added meta-info for all docs

translation of the BEM-referense is added
Replace article -> articles
New articles (libraries)
Changed markdown to parse md to html
Categories for articles
Update migration.en.meta.json
Update migration.ru.meta.json
fix invalid category reference for i-bem-js articles
Add links for changelog
Merge pull request #312 from sipayRT/issues/311@v1

Added meta-data for bem.info