* Fixed GenomeLocSortedSet.add() to ensure that overlapping intervals are detected and an exception is thrown.
* Fixed GenomeLocSortedSet.addRegion() by merging it with the add() method; it now produces sorted inputs in all cases.
* Cleaned up duplicated code throughout the engine to create a list of intervals over all contigs.
* Added more unit tests for add functionality of GLSS.
* Resolves GSA-775.