Add the Functional module.
Add the Core module and group logicals together.
Add the Foldable module.
Start writing unit tests for quick/*.
Unit test the Logical module.
Fix the Foldable module.
Remove bugged flip_* versions of typeclasses.

They are broken because they only work when the operation they
flip is commutative. I can't believe I did not see this at first.
Add common_datatype.
Use common_datatype in Comparable and Orderable.
Add the cast metafunction class.
Pass method arguments as-is.
Remove Doxygen group Tags.
Don't use README as main page for Doxygen.
Add the Monoid, Group, Ring and Field typeclasses.
Add the default_<> dummy type.
Make integral_c an Integer.
Add the IntegralDomain typeclass.
Clean up some old stuff.
Rename integral_c to integer_c.
Add the Rational datatype.