Improve Dockerfile for global modules

[aklenik]

Signed-off-by: Attila Klenik [email protected]

• The core module is installed explicitly, so it's placed at the root of the global node_modules folder. The other core deps are deduped to this.
• NODE_PATH is set to the global node_modules folder, so external modules (like the workload module) can require it without explicitly installing it as its own dependency (and possibly breaking singleton patterns, since that'll be a different module).

[nklincoln]

lgtm 👍