AphrontNoteView

Summary: This is supposed to look a lot like the way Remarkup renders a block of code, so you can render some out of context message inside another container.  For example in Releeph, it renders a message someone has associated with a Releeph request.

Test Plan:
I've added an abstract uiexample, but the use case in Releeph is more explanatory:

{F33900}

Reviewers: epriestley, chad

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2094

Differential Revision: https://secure.phabricator.com/D5125