Update the source distribution to build only the Crowd source

This is a change to our source distribution that will still allow modification of Crowd itself while reducing the complexity of the build.

The source distribution currently includes the source for Crowd along with a couple of other dependent modules that are combined into a single reactor.

After this change, only Crowd's source will be built; other modules will have their -sources jars included for inspection, but those modules won't be built from source by the build.sh script.