Fixes typo in test name.
Adds the concept of Infinity to SC.IndexSet.  Although, the number of indexes will always be constrained to Number.MAX_SIZE, attempting to create a range even in the several hundreds of thousands would freeze the client, because it will attempt to generate hints every 256 items.  Instead we can use the concept of infinity and don't try to hint the infinite range.  For one, this allows for infinite arrays and infinite lists to be possible without using really large numbers that are very slow to hint.

Includes unit tests.