Multiple value tests on same element

[mattgarrish]

I thought we'd addressed this in an earlier PR, but looks like it didn't get implemented.

The xpath for non_textual_content_images in 4.2.2 can be reduced to:

/onix:ONIXMessage/onix:Product/onix:DescriptiveDetail[onix:PrimaryContentType = ("07", "18", "19", "12", "49", "20") or onix:ProductContentType = ("07", "18", "19", "12", "49", "20")]

and the non_textual_content_audio* ones in 4.4.2 to

/onix:ONIXMessage/onix:Product/onix:DescriptiveDetail[onix:PrimaryContentType = ("21", "22") or onix:ProductContentType = ("21", "22")]

and

/onix:ONIXMessage/onix:Product/onix:DescriptiveDetail[onix:PrimaryContentType = ("06", "25", "26", "27", "28", "29", "30") or onix:ProductContentType = ("06", "25", "26", "27", "28", "29", "30")]