Fixed bug when calculating deadlines for algorithms where the ALAP schedule contained laps.
Replaced all startswith checks with isinstance for operations.
Updated SchedulingGUI to show "∞" instead of maximum integer for forward and backward slack.
Added enforcing of execution time in ListScheduler and added test to check that latency-offsets and execution times will raise Exceptions if missing.
Updated ALAP scheduler to adjust scheduling time if a "gap" appears in the start of the schedule.
Closes: #324 (closed) #322 (closed) #318 (closed) #277 (closed) #327 (closed)
