Fix for binary glTFs storing CRN and KTX textures

[lilleyse]

Bug report and fix from the forum, with some modifications: https://groups.google.com/forum/#!topic/cesium-dev/02M8ho6hONo.

[cesium-concierge]

@lilleyse thanks for the pull request!

I noticed that a file in ThirdParty/ or Source/ThirdParty/ has been added or modified. Please verify that it has a section in LICENSE.md and that its license information is up to date with this new version. Once you do, please confirm by commenting on this pull request.

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[pjcozzi]

Does this need new unit tests?

[lilleyse]

Improved the tests a bit. They were able to pass before because the default texture was being used.

[pjcozzi]

Are these CI failures related?

  Core/sampleTerrain
    ✗ queries heights from Small Terrain
	Expected undefined to be greater than 5000.
	    at Specs/Core/sampleTerrainSpec.js:42:41
	    at Promise.then (Source/ThirdParty/when.js:196:34)
	    at Source/ThirdParty/when.js:297:13
	    at processQueue (Source/ThirdParty/when.js:647:4)
	    at _resolve (Source/ThirdParty/when.js:333:4)
	Expected undefined to be less than 10000.
	    at Specs/Core/sampleTerrainSpec.js:43:41
	    at Promise.then (Source/ThirdParty/when.js:196:34)
	    at Source/ThirdParty/when.js:297:13
	    at processQueue (Source/ThirdParty/when.js:647:4)
	    at _resolve (Source/ThirdParty/when.js:333:4)
	Expected undefined to be greater than 5000.
	    at Specs/Core/sampleTerrainSpec.js:44:41
	    at Promise.then (Source/ThirdParty/when.js:196:34)
	    at Source/ThirdParty/when.js:297:13
	    at processQueue (Source/ThirdParty/when.js:647:4)
	    at _resolve (Source/ThirdParty/when.js:333:4)
	Expected undefined to be less than 10000.
	    at Specs/Core/sampleTerrainSpec.js:45:41
	    at Promise.then (Source/ThirdParty/when.js:196:34)
	    at Source/ThirdParty/when.js:297:13
	    at processQueue (Source/ThirdParty/when.js:647:4)
	    at _resolve (Source/ThirdParty/when.js:333:4)

https://travis-ci.org/AnalyticalGraphicsInc/cesium/builds/266571774?utm_source=github_status&utm_medium=notification

[lilleyse]

It also fails on master locally, so not related.

[cesium-concierge]

Congratulations on closing the issue! I found these Cesium forum links in the comments above:

• https://groups.google.com/forum/#!topic/cesium-dev/02M8ho6hONo

If this issue affects any of these threads, please post a comment like the following:

The issue at #5753 has just been closed and may resolve your issue. Look for the change in the next stable release of Cesium!
Or get it now in the master branch on GitHub https://github.com/AnalyticalGraphicsInc/cesium

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