Alikeness of Functions

[brodieG]

Currently signature is required to be a possible generic to a method. In the future we might relax that or at least provide a mode that allows a more relaxed fit.

This all came from the valaddin example where we wanted to add checks that we ensured would lead to two argument functions, but they failed because the function arguments were incorrect.

Thinking about it further it seems that a function should be able to be called with the argument specified, so the # of arguments only deal probably is not a good idea. We could however provide a special object along the lines of elist and vlist being considered in #29 that would vet purely the number of arguments.