Simplify precondition generics.

[metasansana]

Currently usage of this module requires a lot of type assertions and type parameter passing, it makes for some unsightly situations often hidden behind .

[metasansana]

Coming back to the record types, there probably isn't any need to track the field level types. The idea behind this module is that once a value passes the checks then we consider it to be valid for the destination type. Whether the checks are sufficient enough is left in the hands of the user. That of course makes the process inherently type unsafe but that in most cases might be an allowable tradeoff for ease of use.

Restrict for example might look like this:

const restrict = <A, B extends object>(value:A) => B

where isRecord should be incorporated because restrict only works on objects.