Add Skip and Limit

[timshannon]

Other databases have options of skip and limit to help with pagination. I'm thinking I'll handle this by adding a Row field selector similar to how you can compare against the Key with bolthold.Key()

So a query may look like this:

bolthold.Where(bolthold.Row()).Ge(0).And(bolthold.Row()).Lt(100))

It allows you to skip and limit.

[timshannon]

While I think bolthold.Row() makes for a better cleaner interface, keeping track of the current row for each index entry along with tracking the row past Seek calls would be impossible, and would mean that implementing Row() correctly would hurt performance. Not worth it. I'll just implement Skip() and Limit() instead.