Moved fake manager creation and initial configuration into the proxy generator (Part I)

This is the first part of PR #372 (we split it up into 2 PRs as mentioned there).

It solves #371 partially, namely that the default behavior is available inside the c'tor call. Therefore it also solves the bug #368 (see the `when_faking_a_class_which_calls_virtual_property_members_in_constructor` test case).
1. I like the remarks.
2. I'm unsure about the interface name. The fact that it's a Provider seems even to me without adding a Lazy on the front. Perhaps I'm just not quite getting the concept. Or maybe I'm not getting the concept because I'm confused about the name.