Update bnd to the 2.1.0 version

The old bnd version used had problems with working with JDK 7 and JDK 8 bytecode, in particular with the _invoke dynamic_ support. 

It's been problematic for the Groovy project, as we haven't been able to osgi-fy the Groovy artifacts with the invoke dynamic compiled classes.

http://issues.gradle.org/browse/GRADLE-2806