LINQ Query Support

I found your sample code very helpful. I discovered, however, I couldn't use NPoco's LINQ query mechanism to filter database objects by an Enumeration type. Something like this could have worked:

```C#
db.Fetch<BlogPost>("where Category = @0", Category.Books.Value);
```

but the strongly-typed LINQ approach seems preferable:

```C#
db.FetchWhere<BlogPost>(x => x.Category == Category.Books);
```

This pull request adds support for the latter.

I also went ahead and removed all the build products, NuGet packages, and user settings files from the repository to avoid merge conflicts. All these files were already covered by the `.gitignore` file.

Let me know if you have any questions. Thanks!