Added default support to DummyValueCreationSession for type Lazy<T>

Based off of the behavior that is defined for Task. Discussed in issue #358.
A tiny thing, and I wouldn't mention it if there weren't other comments for this file, but the FakeItEasy standard is to put the usings inside the namespace, sorted (with System* ones coming first), so this could go on line 6, if you don't mind. It's something we maintainers often clean up after a merge, but you seem nice, so I figure I'd mention it anyhow. If you pay strict attention to the warnings when you build, you'll see one complaining about it.