Reasonable naming scheme for functions

[andrejbauer]

The various functions in Value have ad-hoc names, for unstance lookup_bound vs. get_bound and get_dynamic vs. get_dyn vs lookup_dynamic. It would be good to have a namign scheme that is less random.

[SkySkimmer]

The monadic bind and variable binding could get confusing as well.

[andrejbauer]

Regarding the bindings, would it make sense to recode pattern matching so that it avoids exceptions and uses a monad? Would that help in reducing the variety of monads we use?

[SkySkimmer]

Matching uses the following which have monadic versions: (matching version | monadic version)

Value.get_bound | Value.lookup_bound
Value.get_dynamic_value | Value.lookup_dynamic_value
Value.push_bound | Value.add_bound
Value.get_signature | Value.lookup_signature
Value.get_constant | Value.lookup_constant
Value.get_env | N/A

In other words, if we convert matching to be in the monad the left side goes away.

Desugar used some redundant functions as well but not after #271.