Alternate implementation for timeline

[jakewmeyer]

While updating the timeline for STP-2, I realized how terrible the current format is to work with, and how inflexible it really is.

Going to change all of them over to a new format that should be easier to iterate over, and easier to display events.

Ex.

{
  "timeline": [
    {
      "event": "Go for propellant load",
      "time": -3180
    },
    {
      "event": "RP-1 loading begins",
      "time": -3000
    },
    {
      "event": "LOX loading begins",
      "time": -2700
    }
  ]
}

Bit more wordy than the previous implementation, but it's easier to iterate, and gives event descriptions out of the box.