Improvement: Consider adding a less verbose method for a single constraint

[yochannah]

Consider this code - when there is only one constraint, wrapping each element in datastructures seems unnecessarily verbose.

 setConstraints(
    paths = c("Gene"),
    operators = c("IN"),
    values = list("PL_Pax6_Targets")
  )

Suggestion
It would be nice to either overridethe method signature for setConstraints to allow something like this

 setConstraints(
    paths = "Gene",
    operators = "IN",
    values = "PL_Pax6_Targets"
  )

or alternatively, if this isn't something that can be done in R, maybe just adding the method setConstraint (note no s at the end) would achieve the same thing.

This is low priority but would probably be easy to implement while fixing more important constraint issues such as #58