Merge branch 'master' into merge

* master: (25 commits)
  Change base class of Uid to ORMObject.
  Add the ORMObject.get() class method.
  Extend ORMObject.validate() to support _id columns.
  Make validation of DBSource less strong.
  Simplify validation of not NULL constraints.
  ValidatorTestCase: test before_update, too.
  Add PoolFile.validate().
  Add classes Validator and ValidatorTestCase.
  Fix documentation.
  JSON: support python 2.5, too.
  Add new class ORMObject and ORMObjectTestCase.
  Refactor the fixture setup in PackageTestCase.
  Improve queries in dbconn.py using with_parent().
  Drop class SrcAssociation.
  Create, test, and improve get_suite_version().
  Create, test, and improve get_newest_source().
  Test and improve package_to_suite().
  Test and Improve source_exists().
  Remove some useless session.flush() calls.
  Test suite_name in test_upload()
  ...