collada2gltf: output bundle path needs to be in url format

Otherwise it does not work on Windows.

It's strange though that input path has to be converted from url to
native path format. At least that was my observation.

Change-Id: Ia8d9e9719d927cab2ae4d928eb8066cab4588281
fix .kmz support on Windows; no idea why this int was unsigned

Change-Id: I08fa1c3956b48bcd65edb74add010fafa17bfe82
collada2gltf: Ignore case of the extension.

Change-Id: If7f39a1a0537c561373137e6a9dcdb22b48037f0