Revert "Add design document for exchanges"

This reverts commit 22bc18372788f9b0c2e34060482127c4216ff526.

Conflicts:
	test/conversation.coffee
Refactor pouch insertion/definition
Split random functions out into library

These may well be insecure, so let's at least keep them all in one
place to make it easy to update them
First cut of conversation registry
Method to allow updating an existing conversation
Rename view
View to return all conversations
Still emit ready if design doc conflicts
Allow removing docs from registry
Expose API to destroy conversation
Expand random lib
Add util lib with validations
Add rough UI to create, delete and list conversations