Auto-launch after deployment of app to App Dev Tool.

Launches after deployment via USB or network.

- Abstracted out http request logic in order to implement launch with the same code.
- Removed old comments from multipart code
- Reorganized `ProgressMonitor` updates and values
- Ignoring `-100` error as it is normal (closed connection) on USB.

Will follow up with a PR to unify the push and launch code into a single method regardless of target.

Fixes #2467 
Please review, @devoncarew and @ussuri 
I think we need to be able to configure GET or POST here. Or perhaps the absence of a payload implies GET?