Maven is now used to update the constants, build the Java code, call make to
build the native library, and run all the tests. I have removed the "install"
and "uninstall" targets; instead, the expectation will be that the JNI library
will be placed somewhere on java.library.path and the JAR file will be used as
usual (e.g. in a downstream Maven project, or placed on the classpath of your
project).
Since Maven is now running our tests, this eliminates the need to bundle test
dependencies in `testdep`, and makes the project structured more like a typical
Java project.
