Moving arduino-connector to /usr/bin during installation

[luigigubello]

In my ArduinoConnector.service the variable WorkingDirectory is set to /home/$USER because the arduino-connector bin file was in my home directory during the installation so install.go set this value for WorkingDirectory (and also for the variables ConditionFileIsExecutable and ExecStart the file install.go used my home directory). It can be better to move arduino-connector bin into a /usr/bin during the installation and use this path in ArduinoConnector.service.