I18n, versionnable and external-schema fix issue

Many changes in this PR, sorry for that, next time I will create one PR for each changes.

 * referenceOnly parameter on external-schema tag work now, if present skipSql is adding on each tables contained in the external schema
 * I18n behavior : does not generate sql if parent table skipSql parameter is set to true
 * versionnable behavior : does not generate sql if parent table skipSql parameter is set to true