CLI output from `functionapp publish` should be machine readable

When publishing a new function app, the output includes important information like Function Names, URLs, etc. These are very important to deployment pipelines and, as such, should be machine readable (e.g. JSON, XML, etc).

Would be beneficial to have a flag (e.g. `--output-format json`) that would output the result of `functionapp publish` in the desired format so it could be `stdin`'d to another process

related: #273

Start at the `functionapp publish` CLI entry point and review the current output, using related issue #273 for context. Define how the requested output format flag should represent the published function names and URLs, then verify that the selected machine-readable output can be piped to another process.

Written by the indexing model from the issue text.