Added functionality to listSets and a fix for strange bug.
Added functionality to listSets and a fix for strange bug.

pm.listsSets() without args or kwargs now acts as if called with
allSets=True. (maya errors if listsSets is called without agrs so
it is safe. The stange bug is what maya (atleast linux-2010) lists
some internal set, which does not exit (objExist returns false)
in the scene - "defaultCreaseDataSet".

assumptionsoup/pymel,juggernate/pymel,leonsooi/pymel,shrtcww/pymel,AtonLerin/pymel,assumptionsoup/pymel,leonsooi/pymel,AtonLerin/pymel,juggernate/pymel,david-lassonde-adsk/pymel,shrtcww/pymel,david-lassonde-adsk/pymel