added large disjoint scale tests

[kubikowski]

added large disjoint scale tests:

Added 2 scale tests to each of the comparisons, and operations scale test suites:

1. 2 disjoint 7.5M element sets: tests function(multiplesOf2, multiplesOf2B).
2. 3 disjoint 5M element sets: tests function(multiplesOf3, multiplesOf3B, multiplesOf3C).

Those 3 new large sets are constructed as follows:

1. multiplesOf2B: the multiples of 2 from 15M to 30M.
2. multiplesOf3B: the multiples of 3 from 15M to 30M.
3. multiplesOf3C: the multiples of 3 from 30M to 45M.

Also, split the large sets scale tests into 2 describes: 2 large sets & 3 large sets.