Remove PowerWeightedMeasure

Unused and untested.

Author: oschulz

src/MeasureBase.jl

@@ -176,7 +176,6 @@ include("combinators/likelihood.jl")
 include("combinators/pointwise.jl")
 include("combinators/restricted.jl")
 include("combinators/smart-constructors.jl")
-include("combinators/powerweighted.jl")
 include("combinators/conditional.jl")
 
 include("standard/stdmeasure.jl")