Eject Simpler.Data classes

Simpler has two concepts - class design and database interaction, and frankly that makes it harder to describe Simpler. Simpler is supposed to be *simpler*, right? I use to debate (with myself) that since most of our projects require database interaction that including the `Simpler.Data` namespace in the Simpler.dll was *simpler*. However, that causes other confusion, for example it leads newcomers to assume that using Simpler means you're choosing to use Simpler.Data classes as well which isn't necessarily true at all.

There's also the fact that there are better options now, such as Dapper (and of course NHibernate). I obviously  like the look of the `Simpler.Data.Db` class API better than Dapper, but it performs better. This could be fixed, but it isn't something I'm personally interested in pursuing. (There are many options besides Dapper, it just happens to be my favorite alternative "micro-ORM".)

This means Simpler 3.* would no longer include the `Simpler.Data` namespace - this pull request removes all the classes. If there is interest to keeping the `Simper.Data` namespace alive (past Simpler 2.*) then I like the following option, but I'm open to anything.

1. Create a new Simpler.Data repo on the https://github.com/ResourceDataInc account, copy Simpler there, delete all non-Data classes, and then add a reference to Simpler.
2. @rlgnak would need to resubmit his https://github.com/gregoryjscott/Simpler/pull/13 that adds Nested Properties to the Simpler.Data repo for review.
3. Setup nuget package for Simpler.Data (or give it a new name).

This will close #16.

Please add comments to this pull request if you have thoughts or questions. Thanks.