Refactored AssemblyElementMaterializerTests

to look like the other Materializer tests.
Added a test case for filtering of input

into AssemblyElementMaterializer<T>. This resolves #31
(https://github.com/ploeh/Albedo/issues/31).
Moved *Materializer files into Refraction folder,

as a first step in refactoring *Materializer into *Refraction. See the
discussion on https://github.com/ploeh/Albedo/issues/24 for more details.
Changed namespaces for types in new Refraction

sub-namespace.
Renamed to IReflectionElementRefraction<T>

from IReflectionElementMaterializer<T>.
Renamed all *Materializer classes to *Refraction.
Renamed Materialize method to Refract.