I figured out how to do it. While it is really not documented there is an accidental hint under section "2. Programming the SODAQ board" at http://www.sodaq.net/#!getting-started/c21ma.
"Pin 6 is normally used for switching power to the Switched row of Grove connectors, but for now we just use it because it has an LED too."
The digital pin 6 powers both the led and the actual grove connectors as well. Here is some sample code.
void setup()
{
pinMode(6, OUTPUT);
Serial.begin(9600);
}
void loop()
{
digitalWrite(6, HIGH); // Turns on both the LED and the power
delay(400);
int value = analogRead(A0); // read your analog sensor that needs power
digitalWrite(6, LOW); // turns off the power
Serial.println(value);
delay(1000);
}