Clarify text state of various parts of app & ways it changes

[ihh]

Different places where the text state (i.e. Bracery source code) is, or may be, stored:

• App, MapView, ParseGraph
• initText (i.e. current state of game), evalText (currently typed in directly), etc.
• localStorage (Save graph in localStorage #56), server (Private namespace ~{username/symbol} exclusively for user, as well as existing public ~symbol which maps to ~{guest/symbol} #35), session (redirect to/from Cognito & Twitter)

Ways it can be initialized on page load:

• by URL
• by view (loading from store, session, or bookmark)
• from localStorage

Ways user can change it:

• by editing graph
• by playing
• by typing directly into the text box
• by clicking reset or reload

Need to clarify all these with a clear conceptual model of how components are organized, including both view components on the page (map, direct editor, player/debugger, app) and model components (store, session, bookmark, URL, localStorage).