Arquivo should boot cleanly off the docker image on a fresh computer

[phillmv]

For example,

• clean up references to the rails master key

  arquivo/bin/start-arquivo

  Line 59 in 2e59b63

  export RAILS_MASTER_KEY=$(cat "$PROJECT_FOLDER"/config/master.key)

• make bin/start-arquivo not need to reference a checked out copy of the codebase