Added bandwidth monitoring feature

There is a change I use in one of my game. It allowed me to track bandwidth usage at bytes level.
Both TCP and UDP connection have his own bandwidth monitor. 

Typical usage:

To get debug output (current bandwidth once per second in console)
client.getTcp().getBandwidth().setDebug(true); 

To retrieve last bandwidth information saved:
client.getTcp().getBandwidth().getLastInformation();

I could also get all the information saved(several seconds at once):
client.getTcp().getBandwidth().getHistory();


By default the history size is set to 120 seconds.


I don't think these classes need to be public API. If you are exposing them solely to call `getBandwidth`, Connection can have `getBandwidthTCP` and `getBandwidthUDP` (or `getMetricsTCP/UDP`).