fix [#34113] operator_menu_enum() - Tooltip not showing descriptions

Python wasn't able to set 'OperatorType.prop', which is used by uiButGetStrInfo().

add 'bl_property' to python operators which is assigned to OperatorType.prop when registering.

(api docs coming next)


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54312 954f8c5b-7b00-dc11-b283-0030488c597c