Added osgi detection and output to file to KarafFeaturesGenTask

I had written a plugin for Karaf features generation, but I liked your overall solution better.  In a fork added OSGi detection for dependencies, so you are not forced to manually list all wrappings.  I also changed the output to a file.  Feel free to use the code, change it, or ignore it completely.  This is my first time contributing directly to a Github project, and first time with a pull request, so my apologies if I messed anything up.