[CB-2213] Added NATIVE_URI to getFileMetadata.
[CB-2213] Added NATIVE_URI to readAsDataURL.
[CB-2213] Added NATIVE_URI to getMetadata.
[CB-2213] Added NATIVE_URI to three methods.

The three methods are FileEntry.remove, FileEntry.setMetadata, and FileReader.readAsText.
[CB-2213] Added the AssetsLibrary framework.
[CB-2213] Added NATIVE_URI to copyTo and moveTo.

Note that moving a file from the assets library isn't allowed since we can't delete from there.
[CB-2213] Updated errors for write and truncate.
[CB-2213] Updated a NATIVE_URI error (getParent).
[CB-2213] Added NATIVE_URI to FileTransfer.upload.
[CB-2213] Skipped image scaling when possible.

Image scaling/conversion is skippable when we're returning a native URI (eg. assets-library://).