AnalyticalGraphicsInc/czml-writer — pull request #46 by mramato (2013-03-20 22:03:29+00:00)
Title: Document level clock definition...

This is probably a little rough around the edges, but is a first cut of a `clock` property for specifying the default clock settings for a czml document or stream. The general idea is that we add `document` as a reserved `id` name and `document` will have unique properties that define "layer-wide" data. (clock being the only one so far).

The only special thing about clock is that none of it's values are time-varying; simply because I don't think it makes any sense. How could start time vary over time? The end result looks like this. When encountered, the client would switch to the new values immediately.

```
{
"id":"document",
"clock":{
"interval":"2013-03-20T21:58:58Z/2013-03-21T21:58:58Z",
"currentTime":"2013-03-21T09:58:58Z",
"step":"SYSTEM_CLOCK_MULTIPLIER",
"multiplier":60.0,
"range":"LOOP_STOP"
}
}
```

I know both me and @emackey need this in our respective projects. Note, this is not related to stored views and tours, which will happen at some point in the future; but I would hope to reuse this clock schema there as well.

CC @kring @shunter