[Improve database requests]

[dedifferentiator]

Database request in dbGetLastDay and other avg calculating functions is implemented too bad, so it's worth to rewrite it, probably using group by, but in this case there are some issues with those days, when there were no data from sensors.

server/dbase.go

Lines 107 to 115 in 8c5b6da

	for i := 0; i < 24; i++ {
	err = db.QueryRow(`SELECT AVG(value_sensor) AS "Average value" FROM "fict_sensors_syn" where id_sensor=$1 and
	time_add >= now() - $2::INTERVAL and time_add <= now() - $3::INTERVAL`, sensId, strconv.Itoa(i+1)+" hour", strconv.Itoa(i)+" hour").Scan(&value)
	if err != nil {
	value = 10000
	}
	valueArr = append(valueArr, math.Round(value*100)/100)
	err = nil
	}

[dedifferentiator]

So now I think it's possible to make valid request (not 30 of them) via window functions. It should be done