* Per-signal `timestamp` due to the nature of USS signals.
* Keeping `message`->`timestamp` so any Listener relying on it being there
isn't tripped up (it's present in all other schemas).
* Specifiy that each `signals` member should have `event` key/value pair
removed.
* Mandate removal of `SystemAddress` from each `signals` member.
* Receivers: Only `horizons` and `odyssey` augmentations are optional.
* Updated examples for these changes.
1. Unix, not DOS, line-endings.
2. `message`->`timestamp` instead of per signal.
3. `message`->`SystemAddress` instead of per signal.
4. `StarSystem` and `StarPos` augmentations now mandatory.