Unkilled background execution of camera manager

[Morelato17]

It may happen, in circumstances to figure out, that the python file launched by the HMI remains alive in background, consuming memory and occupying cameras. This becomes evident when the next time another instance of the camera manager is launched, the log says something like "IDS init failed; missing data streams". This means the camera is already in use

• Brainstorm possible unhandled scenarios;
• Improve exception message to suggest killing the process manually

[Morelato17]

Possible unhandled scenario: debugger crashes and application is manually stopped to fix problems: this lets the python instance alive;

theoretically, a released .exe should handle correct closeup even by crashing but who knows...how to test?