Remove deprecated properties from the adding of the Resource class

[tfili]

Remove functions:

• loadImage
• loadArrayBuffer
• loadblob
• loadImageViaBlob
• loadJson
• loadJsonp
• loadText
• loadWithXhr
• loadXML

Removed deprecation of parameters:

• loadCRN
• loadKTX
• ArcGisMapServerImageryProvider
• BingMapsImageryProvider
• GoogleEarthEnterpriseMapsProvider
• GoogleEarthEnterpriseImageryProvider
• MapboxImageryProvider
• SingleTileImageryProvider
• UrlTemplateImageryProvider
• WebMapServiceImageryProvider
• WebMapTileServiceImageryProvider
• createOpenStreetMapImageryProvider
• createTileMapServiceImageryProvider
• ImageryProvider
• CesiumTerrainProvider
• GoogleEarthEnterpriseTerrainProvider
• GoogleEarthEnterpriseMetadata
• Model
• Cesium3DTileset
• CzmlDataSource
• KmlDataSource

Resource class cleanup

• loadImage method - allowCrossOrigin parameter.
• createIfNeeded method can probably have the options parameter removed. It was there to more easily handle URL strings with a bunch of options specified to the parent classes instead of the to the Resource. Removing all these deprecated properties should remove the need for it.
• Move all the specs for the load* functions to the specs for the Resource class.

[thw0rted]

@tfili you closed this but createOpenStreetMapImageryProvider still takes a string for the URL, meaning you can't load it through a proxy. I can open a separate issue if you like.

[tfili]

@thw0rted Just looking at it quickly, I think it should work if you pass a Resource instance in as the url. It should just be a documentation tweak, if you want to write up an issue or open a PR.

[thw0rted]

Looks like somebody beat you to it in #8079. Maybe @ProjectBarks would like to update the docs to match the fixes he made? I'll drop a comment there.