CORE-1617 dropProcedure change

Added new dropProcedure change and modifed existing createProcedure change to have a custom CreateProcedureStatement and Generator. Also created StoredProcedure database object to define modified object
CORE-1617 dropProcedure change

Added new dropProcedure change and new createProcedure attributes to xsd
CORE-1618 Support defining createProcedure body in an external file