Basic Gradle Build

[geoffballinger]

First baby steps towards a gradle based build system.

No impact on the current bob/eclipse side of things.

Set of five linked PRs:

• https://github.com/good-loop/code/pull/41
• https://github.com/good-loop/open-code/pull/73
• https://github.com/good-loop/elasticsearch-java-client/pull/16
• https://github.com/winterstein/flexi-gson/pull/2
• https://github.com/winterstein/JTwitter/pull/13