[JS] updated radio-node README: mvn has to be run in joynr root
[JS] updated radio-node README: mvn has to be run in joynr root

Change-Id: I2640015fca005aff2f89def8fa4b5070013feb9a

bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,clive-jevons/joynr,clive-jevons/joynr