In order of decreasing significance:
* Move addition of all files later to avoid premature build cache
invalidation
* Add separate instructions to copy over files needed earlier
* Change deprecated MAINTAINER instruction to LABEL maintainer
* Change ADD to COPY, as ADD apparently behaves weirdly in some cases
* Alphabetize dependencies for readability
Certain evennia commands, such as the server command, rely upon
ps to run correctly. Unfortunately, alpine uses the BusyBox ps command,
which is somewhat idiosyncratic in its option handling. Adding
the procps dependency installs a more standard ps command, allowing
server maintenance commands to work correctly. This fixes#1635.
For further background, see gliderlabs/docker-alpine#173.
