Update NEWS and CHANGES
Update to airbase 21
[maven-release-plugin] prepare release 0.89
[maven-release-plugin] prepare for next development iteration
Add abstract event client class
Update NEWS and CHANGES
[maven-release-plugin] prepare release 0.90
[maven-release-plugin] prepare for next development iteration
Do not include dependencies from zip files in lib dir

Zip files are not code and should not be included in the lib dir of an
assembly.  Also, transitive dependencies from zip files should not be
considered.
Update NEWS and CHANGES
[maven-release-plugin] prepare release 0.91
[maven-release-plugin] prepare for next development iteration