Potentially remove support for Ignore Extra Elements

[Turnerj]

I've been thinking about this - it might not actually be necessary to have this support. The driver requires it because of the idea that you might be overwriting things you didn't intend to. Technically though, MongoFramework does partial writes anyway so if your entity doesn't have all the fields that the collection has, it doesn't matter as only the fields you have are set.

I'd still have extra elements support in MongoFramework - that is the support to retrieve non-typed fields from the DB into your model. These would also be saved back to the DB too like normal - it is just removing the ability to ignore them because that would be the default behaviour anyway rather than an actual problem.