Docs 2018.2 (#8188)
* User guide: reorder languages list.
Reorder languages list to follow sorted order based on languages. When appropriate, list locales in braces.
* User guide and what's new: add Mongolian and Swiss German to list of new languages.
* What's new: linguistics and issue number fixes.
* What's new: linguistic fixes.
* User guide: linguistics, settings category descriptions.
Added descriptions for categories for ones that does not feature it (for consistency purposes). Also, did some linguistic fixes.
