Change asset upload to use data rather than file

[chrisbianca]

So unfortunately, it seems that the security permissions for real devices are different from the simulator. Having installed my asset change PR to an actual device this morning, it turns out that trying to upload gives a permission denied error, despite having CameraRoll permissions.

To work around this, I have changed the upload method to use putData instead of putFile and have loaded the data using the Photo library rather than relying on Firebase to resolve the filename to the data (which is where the permissions error occurred).

Sorry for not testing thoroughly enough on the first pull request, but I hadn't expected the simulator to be so different from a real device.

[auser]

Thanks for the follow-up PR. I'll try to get this in tonight.

[seantempesta]

Is this related to this error I'm getting?

Exception '[<NSError 0x6000004444a0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key name.' was thrown while invoking uploadFile on target FirestackStorage with params (
    "<null>",
    "test.jpg",
    "Users/sean/Library/Developer/CoreSimulator/Devices/5E11E987-C50A-40\U2026BCA-C0F2BAC1280C/Documents/images/442C4A2E-E3D1-487B-9712-1C485982F21E.jpg",
        {
        contentEncoding = base64;
        contentType = "image/jpeg";
    },
    315
)