Request for enhancement

As an administrator , I want to use the libpwquality credit system so that have more control over the required character types than just the number of classes present.

libpwquality provides four credits: dcredit, lcredit, ucredit and ocredit for digits, uppers, lowers and others.

A negative credit sets the minimum number of characters for that credit type.
A 0 value, the default, is a no-op.
A positive value is a credit towards reducing the maximum password length required.