Cleanup old stream stuff

/cc @wheresrhys @kaelig @laurent-muchacho @commuterjoy 

- Remove anything stream related from Grumman to avoid confusion!
- Rename article-card classes to article so it doesn't clash with cards
- Bring in template copying from dobi
This one shouldn't actually be here (leftover from stream version) so will delete.
@wheresrhys suggested same for the down arrow in stream for Core experience (href going to article) - but I think for core experience we should maybe not have the button , and keep it expanded by default?