Make it possible to exclude sub-modules

[amanica]

Hi,
I've tried all the exclude options in aggregate-download-licenses, but they only seem to work on the the dependent artifacts and not the actual maven sub-modules. I looked a bit at the source code too, but it seems there is no way to filter out reactor modules.

My use case:
I wanted to create a sub-module to be re-used for tests in other modules, and I need to exclude all test dependencies from aggregate-download-licenses. But since my test library brings in dependencies under compile scope, they make it into the license report which I don't want.
Unfortunately because of maven limitations, using the test-jar is not ideal either as it does not bring in transitive dependencies:
https://maven.apache.org/plugins/maven-jar-plugin/examples/create-test-jar.html

[slawekjaranowski]

Should be easy to implements exclusion for specific module.

https://github.com/mojohaus/license-maven-plugin/blob/master/src/main/java/org/codehaus/mojo/license/AggregateDownloadLicensesMojo.java#L129-L137