updated to gradle-bundle-plugin 0.6.2 and extracted bnd config to bnd.bnd

Now that upstream changes to 0.6.2 have been merged we can now pull all the bnd configuration out of the hard to read gradle scripts and into its native bnd.bnd format.  Now those developers using bndtools can use the nice editor and have a better developer experience.

this does make our gradle builds slightly more complicated in that there are now 2 build files, build.gradle and bnd.bnd but I think the tradeoff is worth it since the bndtools are quite nice.