Add Built-Date and Implementation-Build to generated manifest
Add plugin to check classpath for duplicate classes/resources
Rename checkstyle.config property to default checkstyle.config.location...

and remove unnecessary checkstyle.skip property
Run checkstyle on src/**/*.{java,groovy,xml,properties} and pom.xml
Checkstyle: check braces around do, else, for, while
Release version 1.1.6