Ensure source folders appear first in the classpath list.

After running the other Classpath Configuration classes the source folders
are out of sequence, causing all sorts of problems looking up source. This
is an attempt to re-order the classpaths.  It hasn't yet been tied into the
code, but here for code review and comment.
Yeah, this is what i meant exactly. Do not worry, all the source folders are provided in the maven model. If one is missing from model for some reason, it will not appear in the classpath either, so it is uninteresting for us.