Support Entity Framework in CreateMapExpression

Hello,

I have made changes to enhance the support for building queries that translate to SQL using the Entity Framework. 

- Allow nested queries that can be mapped to SQL. 
- Added support for mapping to Arrays using CreateMapExpression.
- Created Unit Test cases for Linq Expressions.

```c#
 Mapper.CreateMap<Entity, EntityViewModel>()
.ForMember(m => m.SubEntityNames, o => o.MapFrom(f => f.SubEntities.Select(e => e.Name)));

 var expression = Mapper.CreateMapExpression<Entity, EntityViewModel>();
```