* Update hooks to use `read -r` and `printf`
This portably avoids any interpretation of backslash escapes by the
shell.
* Support running make_tc_task elsewhere
* Add a test for backslashes in task descriptions
- Removed the ability for hooks to add tasks, or modify tasks that are outside
the context of the current event. This makes hooks a local mechanism that
operates only on local changes. Modifications/additions coming in via sync
command are not processed by hooks.
