adding cumsum benchmark
Add begin/size arguments for inner/outer scan
Inner fold step returns a value instead of writing in ref
Some changes in scalar scan
Add scan spawners
Add scan workers
Add dispatched inner_scan/outer_scan for shared memory
Fix inner_scan_step
Fix shared_memory inner_scan
Add hpx cumsum unit test
Fix parallel_scan, the spaner returns the reduced value
Remove some commented lines
Scan spawner work for all runtimes
Uncomment transform spawner calls
Remove a temporary
Take correct size
Merge branch 'parallel_scan' of https://github.com/MetaScale/nt2 into parallel_scan
Change grainsizes