Refactor CodeGenerator to facilitate the addition of backend-jvstm-common
Add backend-jvstm-common

  * This backend contains code that is common to JVSTM-based backends
  * Some refactorings in CodeGenerator
  * Since a VBox in FF holds the owner and the slotName, remove that duplicate
    information from method's parameters.
  * Add API for generic key-value storage support
  * Add common JVSTMBackend manager
[backend-jvstm-common] remove commented code in jvstmcodegenerator
[backend-jvstm-common] tx+oids+domainclassinfo
[backend-jvstm-common] Add code to ensure FenixFrameworkData initialization
[backend-jvstm-common] replace Error by RuntimeException in withTxNoException
[backend-jvstm-common] Invoke ensureDomainRoot during bootstrap
Add backend-jvstm-common to parent POM
Update maven-surefire-plugin to run parallel tests
Add test-backend-jvstm-common
[test-backend-jvstm-common] add more DML tests for jvstm-common
Merge pull request #91 from smmf/feature/backend-jvstm-common

This merge adds the jvstm-common backend, from which we expect to derive all the JVSTM-based backends. For the time being, the jvstm-ojb backend remains independent.