Add a default port to ESPRESSO_SEQUENCER_API_PORT

[Ancient123]

To reduce the number of required options to launch a basic sequencer docker, we want to set ESPRESSO_SEQUENCER_API_PORT to a sane default. Port 80 chosen since the API communicates over http.

[jparr721]

Won't this require sudo to bind on startup?

[Ancient123]

Or it can be set to a different port. This shouldn't have a negative effect on docker binding either.

We could make it 8080 instead if we think that is better

[tbro]

Slight preference for 8080 over 80.