ensure backwards compatibility for previous jpdl versions

1) set up continuous integration job that runs the test suite using every previous parser version

2) update release documentation.

• add version to matrix in jbpm4-parsers hudson job
• update/add version to JpdlParser

3) store the deployed version in the db. calculate the version based on the namespace or on the jbpm library version at the time of deployment

4) review test suite. ensure that most tests will be run against every jpdl version

5) install tests for all version dependent parsing behaviour.