Implement itests for start/restart/stop server operation

[olkornii]

1. Start the server : Download/Create server -> context menu -> start server -> verify that the server has started (for example localhost:8080 and console output "Server startup in [618] milliseconds")
2. Restart the server: Start the server -> context menu -> Restart server -> verify that server has started
3. Stop the server: Start the server -> context menu -> Stop server -> verify server has stopped

More info: https://docs.google.com/spreadsheets/d/1-ASTHHyzTl3lYJn3NkI-vzEhe9fwNQ1IPgUrmEFKrnk/edit#gid=0

[olkornii]

Would be better to implement #131 before this one.