Add some private Model instance methods to some some plugins easier
Add some private Model instance methods to some some plugins easier

This adds _delete, _delete_dataset, and _update_dataset private
methods, allowing more granularity when overriding in plugins.

yazshel/sequel,beni55/sequel,gferguson-gd/sequel,gferguson-gd/sequel,Marketcircle/sequel,t-morgan/sequel,knut2/sequel,nju520/sequel,offshore-safety/sequel,tmm1/sequel,bigfix/sequel,nicohvi/sequel,pfarrell/sequel,knut2/sequel,davidbegin/sequel,nju520/sequel,dennis-d/custom_sequel,seeARMS/sequel,t-morgan/sequel,mpalmer/sequel,nicohvi/sequel,mpalmer/sequel,davidbegin/sequel,freshpay/sequel,yazshel/sequel,offshore-safety/sequel,uhoh-itsmaciek/sequel,reubano/sequel,reubano/sequel,seeARMS/sequel,uhoh-itsmaciek/sequel,freshpay/sequel,offshore-safety/sequel,chef/sequel,dennis-d/custom_sequel,beni55/sequel,pfarrell/sequel