Telegesis scan for quietest channel

[triller-telekom]

Related to #958 I like to propose an implementation for Telegesis similar to #1003 for Ember.

Passing the channel ZigBeeChannel.UNKNOWN to the ZigbeeNetworkManager#setZigBeeChannel() method now triggers a network scan and select the quietest channel.

Since Ember has already a resttriction in place for the 2GHz channels, see

com.zsmartsystems.zigbee/com.zsmartsystems.zigbee.dongle.ember/src/main/java/com/zsmartsystems/zigbee/dongle/ember/ZigBeeDongleEzsp.java

Lines 993 to 1000 in 73355bb

	public ZigBeeStatus setZigBeeChannel(ZigBeeChannel channel) {
	if (channel != ZigBeeChannel.UNKNOWN && (ZigBeeChannelMask.CHANNEL_MASK_2GHZ & channel.getMask()) == 0) {
	logger.debug("Unable to set channel outside of 2.4GHz channels: {}", channel);
	return ZigBeeStatus.INVALID_ARGUMENTS;
	}
	networkParameters.setRadioChannel(channel.getChannel());
	return ZigBeeStatus.SUCCESS;
	}

I am also doing a scan for the 2Ghz channels only, in the Telegesis implementation.

To be able to implement something like this, I need to get access to the private class ScanResult insideTelegesisEnergyScanCommand. I have changed the code generator to make those classes public in general, but I am not sure if this is a feasible solution.

Also I have fixed an issue in the autocoder that I introduced with #1007. because the "AT" was removed it crashed with an StringIndexOutOfBoundEexception.