I try to convert strings to integers so the configuration is less
awkward. Nix doesn't do `0x______` integers. So since colours are never
written in base ten, let's allow strings.
The splash is now an application that should be started and forked from.
Once started, it will listen for messages on a ZeroMQ socket reporting
progress.
The current protocol is extremely simple, reporting (optional) label,
and reporting a progress amount.
Additionally, it responds to a string commant ("quit") to quit as
needed.
