… for `docker images`.
This deprecates the `filter` param for the `/images` endpoint and make a
new filter called `reference` to replace it. It does change the CLI
side (still possible to do `docker images busybox:musl`) but changes the
cli code to use the filter instead (so that `docker images --filter
busybox:musl` and `docker images busybox:musl` act the same).
Signed-off-by: Vincent Demeester <vincent@sbr.pm>