Miscellaneous Maven improvements

There are numerous changes needed to help fix the Maven build, in order to conform to Maven conventions, and to integrate better with tooling that understands Maven (such as Eclipse M2E).

In particular, the fatjar and full-build profiles seem to be in conflict with one another.
Also, the directory structure for the zookeeper-it module is broken, and the docs module is incorrectly configured for jar packaging, which makes it unnecessarily activate java plugin bindings for the default lifecycle.

There are also other minor issues, such as javadoc being too noisy, maven-assembly-plugin, and maven-antrun-plugin warnings, as well as unnecessary profiles.