Bump groovy version to 2.3.4 from 1.8.6

- And groovy-eclipse-compiler to 2.9.0-01 from 2.7.0-01
- And groovy-eclipse-batch to 2.3.4-01 from 1.8.6-01

Motivated by https://github.com/apache/incubator-brooklyn/pull/320, which incorrectly has a Java compilation error when compiled with Groovy 1.8.6 compiler.