Stock web app

[gwk]

Under pithy/web/stock/ create a basic web app using uvicorn and starlette.

• app.py: provide def app() -> Starlette: ... function to create a starlette app with demo routes, a main() function to run the app via uvicorn.
• db.py: provide a Database class that wraps a pithy.sqlite connection.
• config.py: provide environment configuration.
• home.py: a simple home page. Should have a generic version for unauthenticated visitors and a personalized version for signed-in users.
• schema.py: a demo pithy.sqlite.schema.Schema including the various stock tables detailed below.
• user.py: simple User, Privilege, and UserPrivilege tables.
• signup.py
• signin.py: password based sign-in.
• select.py: a SelectApp endpoint for viewing the database.