added code for multiple BCs per sideset

[eparish1]

Fixed a few things for op-inf when we have multiple BCs on a sideset and fixed a few things that I missed in the merge.

*I see that the unit tests are failing for all branches right now, so I'm not sure what we want to do for merges at this point.

[ikalash]

I think the failures are my fault! I will fix this. Sorry about this, I have been restructuring some of the tests.

[ikalash]

I just fixed the failing tests. My apologies again for breaking them!

[lxmota]

I don't think it's your fault. There is an issue on MacOS that flags a missing file in error that I'm trying to fix.

[ikalash]

I don't think it's your fault. There is an issue on MacOS that flags a missing file in error that I'm trying to fix.

Part of it was my fault. I rearranged some of the tests dirs when I added the input files for the new cylinder problem and forgot to update the tests .jl files accordingly.

I didn't run tests before pushing b/c I was not changing anything in the code, but forgot that the dir structure of the tests needs to be updated. That's how the bug got pushed.