cmd/modify/port: add command to add/remove port forward

Add a new storj-up command that allows for adding and removing port forward settings.

Change-Id: I84f341c3e6686845941bd72d8e1f48cea45ebe08

Update README.md (#84)

image: bump default versions

Change-Id: I33a3540bcafaed005657579eb4a36e4bafd9eae8

build: enable arm64 builds for releases

Change-Id: If70fdc4a58e3727204f0c6b4b9b23c59f6c56810