Add liftSqlPersistMPool function
Add liftSqlPersistMPool function

For it's use case and motivation see #503.

plow-technologies/persistent,pseudonom/persistent,gbwey/persistent,rdnetto/persistent,psibi/persistent,pseudonom/persistent,creichert/persistent,rdnetto/persistent,bitemyapp/persistent,erikd/persistent,gbwey/persistent,naushadh/persistent,paul-rouse/persistent,yesodweb/persistent,gbwey/persistent