Restrict Infinite Parameters to only use Arrays

[pulsipher]

Currently, we allow multi-dimensional infinite parameters to be arbitrary JuMP containers. This adds quite a bit of complexity (e.g., with the use of VectorTuples) and leads to some ambiguous typing. Also, it is not immediately obvious to me when we would actually want to use other containers. Hence, it would be worth it to try out this change to see what performance increases it gives us. From there, we can decide if we should make this change permanent.