Formatter and license headers

I've added the plugin we use for ead/mokap to get a consistent code style, and also other that adds a license header automatically to each source file.

To keep code clean styled, we have to invoke mvn clean install always before submitting the code.

Btw, I've initially selected Apache2.0 license, but we could pick any other license we may like. Opinions?

Note: This is PR #21 - for unknown reasons, new commits were not being shown as part of the PR, so I closed it and reopened it

Closes #19