Consistent ResolveUsing and ConvertUsing interfaces

Commit 8b3bc9367e2607686a72d79a47165b1765048438 (described in AutoMapper/AutoMapper/#445) added an option to do ResolveUsing with a delegate that accepts ResolutionResult. I further extended this with an option of a delegate that accepts (ResolutionResult, Source).

I also added (in fact, just pushed to public) same overloads for ConvertUsing.