Add simple Main class for testing from an IDE
wip add todo
WIP: interval tree
wip: use intervaltree
wip: try to speed fusion up
WIP: pre-compute overlapping tiles to define iteration order
WIP: more work on driving fusion by overlapping tiles
WIP: eliminate border overlap of split intervals
WIP: bug fixes
WIP: more bug fixes

Not 100% sure the iteration bounds are correct yet.
WIP Clean up code