- IOAddress::increase() simplified
 - getLeasesCount renamed to getPoolCapacity
 - removed several intermediate variables

 - increaseAddress renamed to increase
 - check that addrsInRange throw when max < min
 - C++ style casts, consts added
 - check that a can be subtracted from b, when a>b
 - documentation for IOAddress::increase, subtract improved
 - couple unnecessary intermediate objects removed

Also fix some issues from the review.