WIP: Functional constraints

[joshua-cogliati-inl]

This pull request is unfinished and put here for commenting.

[niharika2999]

Some comments after looking at the branch. (My biggest question in here is if this should handle non-2d data.)

I think we are sticking to 2-D data as of now but would like to introduce the handling of 3-D data in the future too.