Fix Maven build to use JARs from public repositories

I'm not sure what someone was trying to do with the Maven build file, but it was uncompilable on JDK 8 for me.  This patch has it using the same JARs the gradle build uses.

If you do want to use copies of JARs committed into version control for some reason, there is a much more straightforward way than `<systemPath>`:  Check them in in the same structure you'd find them in underneath `~/.m2/repository`, then have a `<repository>` entry whose url is, e.g. `file:///../fakeRepo`.  Maven will play much more nicely with that.