When date range is inferior to the sampling range, get the min-max values on both sides

[karlcow]

Currently the slice API is sending the data for the range which has been requested. If we are in between two data points, the slice is empty. That's not right. Data exists but there are not represented.

Let's say there is
t₀ < t₁(d) < t₂ < t₃ < t₄(d) < t₅

• t₁(d) and t₄(d) are data points.
• t₂ and t₃ represents the request range

We request the range from=t₂&to=t₃, where there is no data point, it would probably be good to get the data from t₁(d) and t₄(d) and return that in the slice.

[karlcow]

This is a bit complex to implement to be effective, but we can probably do it.

[karlcow]

So I tried today to make it as simple as possible without too much recursion. I think we need to wait for the DB, that would be a lot more effective than trying to manage list slicing. :)