Smoothing

[MrUrq]

Smoothing added as optional input. Interface which is dispatching on keyword argument type, as previously discussed, was not possible due to method being overwritten when working with keywords.
Ref: #9498, discourse

julia> f(;x::T) where {T<:Real}= println("Real")
f (generic function with 1 method)

julia> f(;x::Bool) = println("Bool")
f (generic function with 1 method)