First cut at DynamicScene/CZML WallGeometry support.
Merge branch 'master' into dynamicScene-wall-geometry
getIntervals should be intervals.
Merge branch 'master' into dynamicPath-crash
Merge remote-tracking branch 'origin/master' into dynamicScene-wall-geometry
Merge remote-tracking branch 'origin/issue1603' into visualizer-refactor

Conflicts:
	Source/DynamicScene/DataSourceDisplay.js
Factor out Visualizer interface

It turns out a `Visualizer` instance only needs `update` and `destroy` functions.  Also start cleaning up other visualizer to conform to the interface and remove uneeded cruft.
Add Navigation Help widget.
Fix incorrect example and destroy method.
Tweak instruction text.
Make help window slightly smaller.
Changes from review.
Fix copy/paste error.
Merge remote-tracking branch 'origin/master' into dynamicScene-wall-geometry
Add Rectangle support to DynamicScene

Still needs specs and cleanup.
Merge branch 'master' into dynamicScene-rectangle
Ongoing DynamicRectangle work

Fix type in CzmlDataSource
Add coordinates property.
Start refactoring Datasource interface

Manually extract all non-dataSourceBrowser specific changes out of the `dataSourceBrowser` branch.
Turn DataSource get methods into ES5 properties.
DynamicRectangle specs and cleanup.