Add Support for Applicative and Normal Order Reduction.

[matthew-mccall]

Is your feature request related to a problem? Please describe.
OASIS currently uses applicative order, which may lead infinite recursion. Normal order can eliminate some cases of infinite recursion at the expense of more resources.

Describe the solution you'd like
We can implement a separate simplify visitor that performs normal order reduction instead.

Describe alternatives you've considered
Making normal/applicative order reduction an option for the simplify visitor will likely complicate the implementation and violate some philosophical principle. Additionally, a separate normal order visitor implementation can simply be excluded from the build for memory and storage constrained devices.

Additional context
Yes, I'm making this PR now after learning about this while studying for proglang