elements in 'mods' adjusted for multi-models

[aaronmberger-nwfsc]

[Backlog comment from table in unofficial NW assessment handbook; originally dated 1/1/2013; has this been dealt with yet?]
Allow user to use different numbers for elements of “mods” list when running multiple models, and ensure that the doMCMCDiags() doesn’t fail in this case (it currently returns an Error Message)