Minor improvements to sub_projects document
Minor improvements to sub_projects document

Let's remove the empty table, to cut down the risk of inconsistency,
and further explain what the list of affiliated project is for.

Change-Id: I3c8970db8de4fc211233903e8220cda72d47e193

asgard-lab/neutron,dhanunjaya/neutron,bigswitch/neutron,huntxu/neutron,glove747/liberty-neutron,javaos74/neutron,openstack/neutron,eonpatapon/neutron,jacknjzhou/neutron,eayunstack/neutron,barnsnake351/neutron,wenhuizhang/neutron,neoareslinux/neutron,igor-toga/local-snat,shahbazn/neutron,mahak/neutron,noironetworks/neutron,paninetworks/neutron,barnsnake351/neutron,klmitch/neutron,openstack/neutron,vivekanand1101/neutron,sebrandon1/neutron,NeCTAR-RC/neutron,sasukeh/neutron,neoareslinux/neutron,adelina-t/neutron,apporc/neutron,huntxu/neutron,skyddv/neutron,jumpojoy/neutron,MaximNevrov/neutron,takeshineshiro/neutron,igor-toga/local-snat,silenci/neutron,openstack/neutron,dims/neutron,mmnelemane/neutron,suneeth51/neutron,yanheven/neutron,bigswitch/neutron,wenhuizhang/neutron,watonyweng/neutron,swdream/neutron,yanheven/neutron,silenci/neutron,MaximNevrov/neutron,chitr/neutron,javaos74/neutron,adelina-t/neutron,takeshineshiro/neutron,klmitch/neutron,mandeepdhami/neutron,jumpojoy/neutron,apporc/neutron,sasukeh/neutron,mandeepdhami/neutron,wolverineav/neutron,cloudbase/neutron,chitr/neutron,jacknjzhou/neutron,cisco-openstack/neutron,JianyuWang/neutron,mattt416/neutron,sebrandon1/neutron,wolverineav/neutron,glove747/liberty-neutron,eonpatapon/neutron,JianyuWang/neutron,shahbazn/neutron,vivekanand1101/neutron,SamYaple/neutron,SamYaple/neutron,mahak/neutron,mahak/neutron,mmnelemane/neutron,cloudbase/neutron,paninetworks/neutron,cisco-openstack/neutron,eayunstack/neutron,skyddv/neutron,noironetworks/neutron,suneeth51/neutron,NeCTAR-RC/neutron,watonyweng/neutron,swdream/neutron,dims/neutron,asgard-lab/neutron,dhanunjaya/neutron,mattt416/neutron