Adds an extension class for check if a collection is sorted.
Changes some small test parameters
Fixes the FindOverlapsSorted method for LCList.
Readds invariant in DIT that checks span.
Reorders findFirst and findLast signatures.
Reorganizes and cleans up NCList
Removes redundant empty check in enumerator
Renames AddHigh to AddLow, as the naming was wrong.
Fixes comments previously containing the word Add
Changes IntervalList in DynamicIntervalTree to keep null lists if only one interval with the same low and high exists. Also removes intervals based on reference equality instead of interval equality.