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 
The email exchange (and the previous bug) mentioned using GET params for this (and probably a GET request, not a POST). So, `/launch?appId=a.b.c` instead of `/launch` and POST params. Is this working using POST?