refactor(upay.server): restructure server code

* remodel flask app
* update to latest upay.common code
* fix tests
fix(logging) update logging config
refactor(scripts) move example scripts into cli module
chore(upay.server) add devserver script + config
fix(appconfig) initialize config from env variable
fix(logging) properly initialize logging
fix(devserver) no longer bootstrap db on devserver start
fix(doc) update README.md with dev instructions