QElement has a (temporarily optional) description
Frame.addElement() sets element description
Frame.getElement() sets element description
QElement description is required
ELementEdge.diff() includes element description
INTEGRATE: ElementEdge.diff() includes element description

* dev:
  ELementEdge.diff() includes element description
  QElement description is required
  Frame.getElement() sets element description
  Frame.addElement() sets element description
  QElement has a (temporarily optional) description
QElement exposes edge constraints
Roadmap updates
QElement.getRawPosition() test cleanup
QElement tests of edge constraints
Initial QElement.diff() (doesn't work on IE 8 yet)
QElement.diff() works on IE 8
QElement.diff() provides useful error for unknown property
Roadmap and changelog updates
Re-enable all tests
INTEGRATE: QElement.diff()

* dev:
  Re-enable all tests
  Roadmap and changelog updates
  QElement.diff() provides useful error for unknown property
  QElement.diff() works on IE 8
  Initial QElement.diff() (doesn't work on IE 8 yet)
  QElement tests of edge constraints
  QElement.getRawPosition() test cleanup
  Roadmap updates
  QElement exposes edge constraints
Merge remote-tracking branch 'upstream/master'