Add util.BuildInformation and buildinfo command

This is a first attempt at #41.

- adam-core: Add git-commit plugin to POM file. The file is generated
is `adam-core/src/main/resources/git.properties` and the info is
available in the object
`edu.berkeley.cs.amplab.adam.core.util.BuildInformation`.
- adam-cli: Add the command `buildinfo`.