Change location of image URI during conversion

The current COLLADA2GLTF converter creates a texture image in the same folder where the glTF file is located (if the option to separate textures is not set). Is it possible to specify the URI of this image during conversion using command line?
For instance, currently we have
```
"images": [
{
"uri": "texture.jpeg"
}
]
```
I'd like to change this to
```
"images": [
{
"uri": "../images/texture.jpeg"
}
]
```

Start by locating the COLLADA2GLTF command-line option handling and the conversion code that generates image URIs. Check how the output glTF path and separated-texture option affect the current URI, then verify that a requested URI produces the desired relative path in the generated images entry.

Written by the indexing model from the issue text.