The Docker quickstart was incorrect and would fail without a correct --address and --access-url

This was discovered during Discord help channel debugging of a blocked user trying to build a workspace on a docker host, where it was hanging at the connecting phase in the agent

Adding an --address 0.0.0.0:7080 and an --access-url http://localhost:7080 unblocked the user.

The previous doc used verbiage such as access URL but was incorrectly specifying the --address or -a instead so there was no way for the workspace agent to communicate with the server. The existing quickstart actually failed at coder server

Also using --address with localhost:7080 does not work either. 127.0.0.1 and 0.0.0.0 work

This PR:

1. Corrects the coder server parameters
2. Updates the screenshots to the new blue-ish coloring