help run mox with docker

in the Dockerfile, allow running on privileged ports and expose those ports.

add a docker-compose.yml with instructions for the quickstart.

fix running imaptest somewhat. after a short while it will hit the rate limiter.

in quickstart, recognize we are running under docker, and print slightly
different commands to set permissions, and skip generating the systemd service
file. als fix cleaning up the right paths during failure in quickstart.

for issue #3

Makefile

@@ -50,7 +50,6 @@ integration-start:
 # run from within "make integration-start"
 integration-test:
 	CGO_ENABLED=0 go test -tags integration
-	go tool cover -html=cover.out -o cover.html
 
 imaptest-build:
 	-MOX_UID=$$(id -u) MOX_GID=$$(id -g) docker-compose -f docker-compose-imaptest.yml build --no-cache mox