Clean up architecture document
Clean up architecture document

This deletes project-wide topics and ensures that the copy reflects our current understanding.

The project-wide pieces of this have moved to:
https://github.com/exercism/docs/blob/master/misc/overview-architecture.md

tejasbubane/exercism.io,RaptorRCX/exercism.io,tejasbubane/exercism.io,RaptorRCX/exercism.io,RaptorRCX/exercism.io,tejasbubane/exercism.io,RaptorRCX/exercism.io,tejasbubane/exercism.io