simplify sensor interface + implement heartbeat

app/AgentScheduler.php

app/Console/Kernel.php

app/Jobs/RunAgent.php

app/Jobs/TriggerHeartbeatAgents.php

app/Sensor.php

app/Sensor/CPUtemperature.php

app/Sensor/ClientVersion.php

app/Sensor/Date.php

app/Sensor/Disks.php

app/Sensor/Heartbeat.php

app/Sensor/Ifconfig.php

app/Sensor/Inodes.php

app/Sensor/ListeningPorts.php

app/Sensor/LoadAvg.php

app/Sensor/MemInfo.php

app/Sensor/Netstat.php

app/Sensor/Perccli.php

app/Sensor/Reboot.php

app/Sensor/Ssacli.php

app/Sensor/USBtemperature.php