backbone message model & view

Created backbone message view
get and set localStorage callbacks

Conflicts:
	app/assets/javascripts/app/views/conversation_view.js

@wip refactor code to incorporate conversations_view

refactor div target for to field with backbone message view

refactor localStorage methods to save message locally

tidy conversations view

change namespace from message to draft for backbone savedraft feature
add changelog for feature: Save blueprint of message on client side using localStorage [#5087]