Make add_foreign_key() reversible.
Make add_foreign_key() reversible.

offshore-safety/sequel,mpalmer/sequel,davidbegin/sequel,yazshel/sequel,Marketcircle/sequel,offshore-safety/sequel,gferguson-gd/sequel,pfarrell/sequel,chef/sequel,nju520/sequel,davidbegin/sequel,nicohvi/sequel,mpalmer/sequel,bigfix/sequel,dennis-d/custom_sequel,knut2/sequel,seeARMS/sequel,uhoh-itsmaciek/sequel,gferguson-gd/sequel,uhoh-itsmaciek/sequel,nicohvi/sequel,seeARMS/sequel,knut2/sequel,beni55/sequel,beni55/sequel,freshpay/sequel,nju520/sequel,freshpay/sequel,yazshel/sequel,reubano/sequel,pfarrell/sequel,t-morgan/sequel,offshore-safety/sequel,reubano/sequel,t-morgan/sequel,dennis-d/custom_sequel