Feature/issue 2682 add 7 parameter ddm pdf #3641

Job	Run time
fwd tests and non-fun mix tests	43m 29s
fwd tests and non-fun mix tests	43m 29s
mix/fun tests 2	3h 35m 31s
mix/fun tests 2	3h 35m 31s
mix/fun tests 1	49m 52s
mix/fun tests 1	3h 49m 29s
prim and rev tests	2h 50m 54s
prim and rev tests	2h 50m 54s
	18h 59m 9s

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