split password-instances into multiple packages

[cdepillabout]

It would be nice if the password-instances packages was split into separate packages, where each package just provided instances for a given Haskell package.

For instance, now the password-instances package provides typeclass instances for the Pass and PassHash datatypes for instances from aeson, http-api-data, and persistent.

It would be nice to break password-instances up into three packages, password-instances-aeson, password-instances-http-api-data, and password-instances-persistent.

The the password-instances package could just re-export all these sub-packages.

[Vlix]

Maybe change the idea to splitting password-instances to password-aeson, password-http-api-data, etc. so they could also include helper functions for working with those specific package combinations?
Would be weird if you'd import Data.Password.Instances.Aeson and then also find functions or values are in that module, no?

[blackheaven]

Handled in #87