RTBKIT-531

This PR brings the BidSwitch exchange connector up to its 2.1 spec (which is based on openrtb 2.2)

*  The Exchange Connector, correctly parses and handle Google traffic -- and in this case, honours the filtering as imposed by Google. 

* It also handle normal Banners.

* However, it does not handle Video and won't, until IponWeb fixes its spec and brings it in accordance with OpenRTB 2.2, which at the time of this writing, will happen in the next few weeks.

Could we put this in an utils class in soa/utils instead of only in this class.

It could be useful for others.