Move "forums" functionality to plugins

[danielnutu]

Idon't know if it's a good idea or not, from a "bloat-ware" perspective and a performance perspective, but can forums be moved to plugins?

Probably add new widget zones used for menus etc.

Similar to #7340 and #7341 and #7368

[RomanovM]

When implement this, we can remove Humanizer package from the core and get rid of the annoying cultures directories in the release.