Reorganize key names for Flags
Reorganize key names for Flags

See flarum/core #265
- Adjusts key names to three-tier namespacing.
- Adds newly extracted strings.
- Adds commenting to match core.

flarum/flarum-ext-english,balkanje/flarum-ext-bosnian1,pladask/flarum-ext-norwegian-bokmal,ogioncz/flarum-ext-czech,flarum/english,pladask/flarum-ext-norwegian-nynorsk,FlarumChina/flarum-ext-simplified-chinese-pro,pladask/flarum-ext-norwegian-bokmal,gtugablue/flarum-ext-portuguese,ogioncz/flarum-ext-czech,raweba/flarum-ext-danish,FlarumChina/flarum-ext-simplified-chinese-pro,pladask/flarum-ext-norwegian-nynorsk