Supply custom plugins as startup

[peterabbott]

It would nice if plugins could be provided as part of the startup instead of copying them after startup.

I can see there is an add-ons directory but that appears to be used for configuring things like the underlying database setup.

Because the folders get created after first startup it makes it difficult to mount a folder. The only options it to extend and use the COPY/RUN commands to put the files in place and then change ownership of the directory tree.

Is there something I have missed? Otherwise I will work on an update to the Dockerfile