Review copying all files vs. selective copy in outer loop ; Also add mvn (/target) and gradle (/build) .dockerignore for samples, starter projects

[scottkurz]

E.g. in the outer loop maven build we're just copying src and pom.xml which is everything standard but what if a user had a 'data' dir or something non-standard? (You'd think that'd be likely just for test but possibly not).

It would be a waste to copy a full /target in but this could be handled via .dockerignore , which we should add anyway.