also, default wsgi config "host" to "localhost" and "port" to "8080" if unset; remove "simple_dc" config

Resolve "prepare Dockerfile and CI for testing image build"

Closes #1

See merge request !1

allow authentication with username only; deliver a RootCollection built from textgrid projects

a `TextgridConfig` class that reads its values from os env; a `EnvNotSetError` that can be raised on config errors; a `TextgridAuth` class that speaks to the textgrid authentication service