added scatter files to gitignore
added scatter files to gitignore

mrquincle/nRF51-ble-bcast-mesh,ihassin/nRF51-ble-bcast-mesh,ihassin/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh