Better interface to smart constructor generation with decapitalized names

[lsrcz]

This pull request adds better interface to smart constructors.

Given the data type

data T a = T1 | T2 a
makeSmartCtor ''T

will now generate

t1 :: (Mergeable (T a), Applicative m, TryMerge m) => m (T a)
t1 = mrgSingle T1
t2 :: (Mergeable (T a), Applicative m, TryMerge m) => a -> m (T a)
t2 = \x -> mrgSingle (T2 x)