"mode" in Participation class should be optional

[btan]

The mode attribute in the constructor for the class Participation should be optional , as specified in http://www.openehr.org/releases/RM/Release-1.0.3/docs/common/common.html#_participation_class
public Participation(
@Attribute(name = "mode", required = true)DvCodedText mode,
..

->
public Participation(
@Attribute(name = "mode")DvCodedText mode,
..