By baking (potentially) multiple pills into an image, we can provide
mainnet vs ropsten images. It is still up to the operator to pass
along the pill path(s) to the entrypoint. For example, using Docker:
docker run --tty urbit -B /share/brass.pill -J /share/ivory.pill ...
The main .image attribute still uses only the solid pill, and image-ropsten
has been provided with brass and ivory pills.
Additionally herb has been added to the image for convenience.
This removes the baked in codedump inspection and wrapper scripts
in favour of downstream tooling overriding this as necessary by
using FROM <image> in their respective dockerfile.
Rather than conditional reconstructing the "urbit/bin/urbit-debug -g"
string everytime using the debug conditional, this information has been
added to the derivation's .meta attribute.
