Improving UTF-8 Support

[tankerkiller125]

The following kinds of bugs regarding UTF-8 are known and require the following kinds of changes/steps:

Problems:

• UTF-8 Usernames are unsupported (utf8-url encoded username url support (simple solve) framework#1949 and not support Arabic letters framework#1990) (fixed via https://github.com/flarum/nicknames)
  • User slugs are currently hard coded to be the username (fixed with Slug Drivers)
• Discussion slugs can not be UTF-8 and transliteration does not work for some languages/cultures (CJK) (Slug transliteration  framework#194) (fixed with slug drivers)
• UTF-8 search is awful (Can't search anything in chinese or japanese framework#2003)
  • In some languages a single character is a single word or even sentences (min search length is now a constant that extensions can override)
• Scrubber date info is hard coded format, will need to localize that.