Improve devc handling for copying entire directories in the Dockerfile

[kathrynkodama]

Currently when there is a copy directory line in the Dockerfile:

COPY --chown=1001:0 /src/main/liberty/config /config

whenever a file is modified within the directory, devc restarts (and rebuilds) the container. In the example above, if generate-features is enabled then on every Java source file change, generated-features.xml will be modified and devc restarts.

Consider better handling so that restarts are not needed every time a file is modified within a copied directory, or special handling when the config directory specifically is copied.