Default orientation for DataSource models

Eventually we plan on providing easy ways to specify orientation for Entity instances; but a small usability improvement in the short term is to just have the model stand up right if no orientation is provided.
WebGL Globe JSON DataSource

1. Add a simple DataSource for WebGL Globe JSON.
2. Make geojson files use `.geojson` extension.
3. Add Sandcastle example.
Add back rotate when space is clicked. Add look when close to the ground and the sky is clicked.
Change look to use the geodesic normal to rotate about. Keep track of looking, panning, or rotating.
Re-add rotate in 3d tests (for mousing over space).
Stay in whatever mode the camera is in until the mouse is released.
Merge remote-tracking branch 'origin/master' into webGL-globe-json
Move WebGLGlobeDataSource into a Sandcastle example

WebGLGlobeDataSource is not popular enough to be part of core Cesium
but is simple enough that it makes a good instructional class.  All of the
code has been moved into a `CustomDataSource` Sandcastle example which
will be linked to and from a website tutorial.
Merge branch 'issue1940' into dataSource-model-defaults
Update default orientation after #1963
Merge remote-tracking branch 'origin/master' into dataSource-model-defaults
Merge remote-tracking branch 'origin/master' into webGL-globe-json

Conflicts:
	Apps/SampleData/ne_110m_lakes.geojson
	Apps/SampleData/ne_110m_land_topo.geojson
	Apps/Sandcastle/gallery/GeoJSON and TopoJSON.html
Fix filename.
Merge remote-tracking branch 'origin/master' into webGL-globe-json

Conflicts:
	Apps/Sandcastle/gallery/GeoJSON and TopoJSON.html
Add rudimentary Timeline documentnation for 1.0

While the Timeline will be completely re-written in the future, we should have at least minor doc for 1.0 (though most things have been marked private).

CC #754
Fix bad if statement.
Reorder 1.0 in CHANGES.md
More 1.0 tweaks in CHANGES.md
Merge pull request #1969 from AnalyticalGraphicsInc/timeline-doc

Add rudimentary Timeline documentation for 1.0
Improve camera for GeoJson example.