Python web launcher

The current version is not perfect as it rely on a timeout instead of waiting
for a given key word in the output.

Issue list:
- When a process ends by itself, it does not release its associated resources
- Process output is not parsed to look for success startup in order to trigger a callback response
- If process crash after starting, the client as no clue and will get a valid response from the server

Change-Id: I330a3a4156a21ff136bcd761338e8ff1df9d1d96
Merge topic 'vtkweb-launcher' into master

ce14c364 Python web launcher