Move logic from load_test_config() to migrations/env.py.

Previously load_test_config was looking for the nonexistent file
'/etc/inboxapp/test-config.json'.  Since it's only called from
migrations/env.py, and since we can assume that migrations on the test DB are
always run by hand from the inbox root directory, move the logic to that file
and simplify it.
Fix a few typos in the docs.
Log stack trace along with slow queries.

Makes it a lot easier to see at a glance where in the code the query is.
Redis configuration + setup.
Bootstrap Redis account sync status info.
Update Redis account sync status info on start-up.
Fix state reporting in report_progress() -> Update folder sync status info.
Calc num_local_updated, num_local_deleted.
Redis schema for per-folder sync status info.
Bootstrap per-folder sync status info.
DB schema changes (FolderSync tables) + migration.
Include timestamp in folder sync status info.
Script for Redis server.
Minor fixes.
Basic Flask app.
Documentation