Unchecks the upstream dependencies checkbox by default
Merge pull request #346 from Houzz/uncheck_upstream

Unchecks the upstream dependencies checkbox by default
Uses less stack-intensive map in renderTasks
Merge pull request #348 from Houzz/stack_safe_map

Uses less stack-intensive map in renderTasks
Issue #338: Add “priority” property to task, to take into account in scheduler.get_work

- implement handling of priority property in Task and CentralPlannerScheduler
- add documentation about task priorities
- add tests for handling priorities in CentralPlannerScheduler