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
Add triggering “event.core.start” when starting a task

- add event.core.start
- minor documentation fix
- add test and fine-tune other event tests a bit