Added gradle as an external build manager

Hi

I don't know if you want it, but I had the need to build org.openntf.domino outside of Eclipse, so I added Gradle, and the Gradle Wrapper to do that. It is not a perfect build yet, for example the osgi plugin builder is not working at the moment, but it builds the main jar file.

If you don't have a Linux machine with Domino 9 installed at /opt/ibm/notes, then you must add a gradle.properties file, either in you user directory, or in the root of the org.openntf.domino folder (same level as gradle.build), and add domino_jre = '<path/to/your/domino>/jvm/lib' there (or change in gradle.build)

By running ./gradlew (or gradlew.bat), it will pull down the necessary components to run, and compile itself. The jar files end up in build/libs/*

regards,
Bjørn Cintra