Allow dumping any schedule from the CLI.

[andriyDev]

Previously, we could only dump the Update schedule from the CLI. Now we can do any schedule.

To make this happen, I also redesigned the CLI slightly. Instead of having flags for each command (--dump-render, --dump-update-schedule), I switched them to look like commands. So now users can do cargo r -- dump-render render.dot or cargo r -- dump-schedule Update update.dot. However this does mean we can't do both at the same time. This seems like a reasonable approach though and makes it easier to extend. For example we can have flags that are only available in specific commands (e.g., filter by system set should only be a valid flag if you're running the dump-schedule command).

In a future PR, I think we can also extend this to support sub-apps with an additional flag to the dump-schedule command.