Add Positive static properties to Range class

[konard]

(1L, long.MaxValue)

Should be replaced with:

Range.PositiveInt64

And used here:
https://github.com/linksplatform/Data.Doublets/blob/5c773e28fb9e0d16b6a611186442bba7f47bf13c/csharp/Platform.Data.Doublets.Tests/OptimalVariantSequenceTests.cs#L150

[uselessgoddess]

If used once. Maybe it's better to create a local constant?

[konard]

If used once. Maybe it's better to create a local constant?

Once we have more than 3 usages in the whole project, we can move it here. So this issue can help track these usages.