Implement timed task in task model
Implement timed task in task builder
Reflect the change to UpdateTask
Modify @lowjoel visitor
Add DEFAULT_START_TIME
Fix the regression caused in test
Modify @lowjoel tests
Reflect the change in adding task/subtasks/dependencies
Implement serialization of start time
Lint fix
Use templated getOrDefault
Merge pull request #341 from evansb/subtask-api

Implement StartTime for timed tasks