Adjust MNView initial version from 1.2 to 2.0

[rogerdahl]

The API docs list MNView as added in 1.2, but OptionList, which is used by listViews() was added in 2.0.

Both Metacat and GMN supports listViews() only in v2.

https://knb.ecoinformatics.org/knb/d1/mn/v1/views
https://knb.ecoinformatics.org/knb/d1/mn/v2/views