Save information about the backend in the zip file?

[blester125]

We should be able to save enough information in the models zip file to figure out what the backend (tf/pyt) is so we shouldn't need to pass --backend (tf|pyt) to the api-examples

[dpressel]

Im moving this out of 2 since its not assigned. If its already being worked, send a PR and reset the milestone to v2