Enhance RelationRegistry docs a little bit
Enhance RelationRegistry docs a little bit

pvcarrera/rom,dekz/rom,Snuff/rom,denyago/rom,vrish88/rom,rom-rb/rom,rom-rb/rom,endash/rom,kwando/rom,pxlpnk/rom,pdswan/rom,rom-rb/rom,dcarral/rom,jeremyf/rom,cored/rom