Tasksched

- Adjust the project start date to the next business day if it's a week-end or a public holiday.
- Fix work plan end date.
- Fix typo "usage" -> "use".
- Fix colors when tasks are split.
- Merge resources and tasks from multiple JSON input files when they have the same `id`.
- Make resource `name` and task `title` optional fields (use `id` by default).
- Add task fields `priority` and `max_resources`.

- Add examples directory.
- Fix merge of JSON configuration files.
- Fix work plan build error on end date if a resource is not used at all.
- Fix read of standard input.
- Convert resource and task id to string.

- First release.