Add Swift Design Principles to CONTRIBUTING.md
Add Swift Design Principles to CONTRIBUTING.md

This is based of work started a few design summits ago [1].

With EC getting close I felt like I could the inspiration.

1. https://etherpad.openstack.org/p/juno_swift_core_principles

Change-Id: I90fa56d67003080fe3d7bc4e0fad053e3b0c8504
Signed-off-by: Thiago da Silva <f23d94b2a735b6193d3882ae31308d2e41e8282b@redhat.com>

gold3bear/swift,tipabu/swift,williamthegrey/swift,bouncestorage/swift,openstack/swift,tipabu/swift,nadeemsyed/swift,bradleypj823/swift,psachin/swift,hurricanerix/swift,Em-Pan/swift,openstack/swift,Akanoa/swift,takeshineshiro/swift,smerritt/swift,clayg/swift,thiagodasilva/swift,hbhdytf/mac2,aerwin3/swift,psachin/swift,bkolli/swift,dencaval/swift,redhat-openstack/swift,daasbank/swift,IPVL/swift-kilo,hbhdytf/mac2,gold3bear/swift,wenhuizhang/swift,mjwtom/swift,bradleypj823/swift,swiftstack/swift,hurricanerix/swift,hurricanerix/swift,rackerlabs/swift,notmyname/swift,matthewoliver/swift,swiftstack/swift,hbhdytf/mac,nadeemsyed/swift,bouncestorage/swift,rackerlabs/swift,hbhdytf/mac2,notmyname/swift,clayg/swift,zackmdavis/swift,levythu/swift,psachin/swift,Em-Pan/swift,AfonsoFGarcia/swift,matthewoliver/swift,clayg/swift,hbhdytf/mac,prashanthpai/swift,wenhuizhang/swift,smerritt/swift,daasbank/swift,nadeemsyed/swift,shibaniahegde/OpenStak_swift,mjzmjz/swift,notmyname/swift,larsbutler/swift,smerritt/swift,matthewoliver/swift,IPVL/swift-kilo,redbo/swift,revoer/keystone-8.0.0,tipabu/swift,mjwtom/swift,williamthegrey/swift,larsbutler/swift,dencaval/swift,mjzmjz/swift,hbhdytf/mac2,notmyname/swift,revoer/keystone-8.0.0,swiftstack/swift,redbo/swift,takeshineshiro/swift,thiagodasilva/swift,shibaniahegde/OpenStak_swift,AfonsoFGarcia/swift,Seagate/swift,openstack/swift,maginatics/swift,psachin/swift,redhat-openstack/swift,tipabu/swift,nadeemsyed/swift,clayg/swift,zackmdavis/swift,aerwin3/swift,iostackproject/IO-Bandwidth-Differentiation,Seagate/swift,hurricanerix/swift,maginatics/swift,levythu/swift,smerritt/swift,iostackproject/IO-Bandwidth-Differentiation,prashanthpai/swift,bkolli/swift,Akanoa/swift,matthewoliver/swift,openstack/swift