Integrate code coverage tooling

[ajvb]

It would be nice to be able to view metrics on how our code coverage is doing across our unit tests. If we have a tool that can support multiple languages to cover contrib, that would be nice, but making sure can see the % coverage of the Java code is the more important piece.

[ajvb]

There is a commit in the branch codecov that adds jacoco code coverage reporting that may be able to be used as a reference - 32f9b3c