Simplify bundle generation / Add io.netty.versions.properties to all JARs

- Fixes #2003 properly
- Instead of using 'bundle' packaging, use 'jar' packaging.  This is
  more robust because some strict build tools fail to retrieve the
  artifacts from a Maven repository unless their packaging is not 'jar'.
- All artifacts now contain META-INF/io.netty.version.properties, which
  provides the detailed information about the build and repository.
- Removed OSGi testsuite temporarily because it gives false errors
  during split package test and examination.
- Add io.netty.util.Version for easy retrieval of version information