Add bit::sort and bit::stable_sort about bitlib

[nmcclatchey]

Note that some efficiency is lost to ensure that elements not found within the range are not compared. Otherwise, the stable_sort algorithm would be:

1. Perform two comparisons (compare(false,true) and compare(true,false)).
2. If both comparisons are true, then the user has violated the contract of std::stable_sort by providing a comparator that does not implement a strict weak ordering. You are now authorized to deploy nasal demons (see "undefined behavior").
3. If neither comparison is true, then all bits are incomparable, and should remain in their current order. Exit.
4. Otherwise, count all set bits (this number will be referred to by the name "num_true")
5. If number of set bits is either 0 or the size of the bit vector, the range is uniform (and thus sorted). Exit.
6. Otherwise, if compare(false,true) evaluated to true, then unset the first size() - num_true bits, and set the final num_true bits.
7. If compare(false,true) evaluated to false, then unset the num_true bits, and set the final size() - num_true bits.