This commit migrates the Airline client to Axis2. The biggest problem was that Axis2 parses date differently and always adds a timezone. As a result, the input string is no longer compliant with ISO 8601. The server has been updated to tolerate both that format and the one with a timezone attached. The build is also simpler as it leverages the Axis2 wsdl2code maven plugin, rather than calling wsdl2java via ant. Closes gh-16