BPMN2 — Lane.partitionElementRef incorrectly defined

Consider swim lanes representing performers.

• The spec states that the Lane.partitionElementRef would reference a Performer. This won't work since Performers are owned by Activities. Hence would result in a different Lane for every Activity.
  Instead the Lane.partitionElementRef should instead reference a Resource, which multiple Performers may reference.

• The XSD defines Lane.partitionElementRef as an IDREF. It should instead be a QName, to allow references to a Resource in a different Definitions file.

(a) On spec pg 285, replace "e.g., all Lanes in a LaneSet defines the Performer element as the partition element, but all with different values" with "e.g., all Lanes in a
LaneSet reference a Resource as the partition element, but each Lane references a different Resource instance".
(b) Update the tLane type in the XSD, replacing
<xsd:attribute name="partitionElementRef" type="xsd:IDREF"/>
with
<xsd:attribute name="partitionElementRef" type="xsd:QName"/>
to allow for Resources in a different definitions file.
(c) The XSD snippet in the spec will also need to be similarly updated.