First draft:
 - added FileVersionUpdate class with a test method for upgrading objects
 - added XSLT for objects
 - modified EnvObjecPersistence so that is tries to update XML files upon loading.
Second try:
 - forced to use xslt 1.0
 - some problems on the template "replace"
Data upgrade feature working. TODO: add proper .xslt files in config/validator/ folder