Fix table and rename QIRBuiltin to QIRExternal

src/qir/QIRTypes.java

src/qir/ast/QIRExternal.java

src/qir/ast/QIRNode.java

src/qir/ast/data/QIRTable.java

src/qir/driver/DBDriver.java

src/qir/driver/IQIRVisitor.java

src/qir/driver/QIRCompileVisitor.java

src/qir/driver/QIRFreeVarsVisitor.java

src/qir/driver/QIRGreedyReduceVisitor.java

src/qir/driver/sql/QIRSQLStringVisitor.java