Improve the rebuilding speed during development by not talking to Discourse

[tanius]

There should be a command line argument that disabled fetching new content from Discourse, because this takes a lot of the rebuilding time and is not needed when just wanting to see design or structure changes during development.

However, this would then require caching the Discourse API responses into some kind of JSON files. And also, rebuilding is fast during development when using the integrated development server. So this might not be worth the effort after all.