Convert cglib to be a maven project

Initial basis to convert cglib to be a maven project, I suspect there would be further work needed to ensure this work correctly but hopefully helps.

- Two tests were disabled for now since they relied on a signed jar file.
- Maven needs to be updated to generate sources/javadoc jar files
can we add sections for `<scm>`, `<issueManagement>`, `<ciManagement>`, and `<distributionManagement>`?

also to make sure we include LICENSE/NOTICE in the jar, can we add a `maven-remote-resources-plugin`?

(i'm basing things to add off guice's pom [https://github.com/google/guice/blob/master/pom.xml].  there might be other things.  no need to do it all in this PR, though.  can do a follow-up that adds them)