Enable local cache for Maven builds

[Maleware]

Currently we need to download maven packages each time we build locally. It would be faster if we could use local cache.

[nightkr]

Just be careful to make sure that mvn installs aren't preserved between builds.. Or you're in for a world of pain.

[lfrancke]

That's a good point. This was a brain fart last night caused by frustration waiting for rebuilds of Hadoop to download the dependencies over and over...

It might not be feasible.