Merge branch 'extendj'

build.gradle

src/main/jastadd/Analysis.jrag

src/main/jastadd/Backend.jadd

src/main/jastadd/RelAst.ast

src/main/jastadd/RelAst.flex

src/main/jastadd/RelAst.parser

src/test/jastadd/constructors/Constructors.jrag

src/test/jastadd/constructors/Constructors.relast

src/test/jastadd/errors/Inheritance.expected

src/test/jastadd/errors/Inheritance.relast

src/test/jastadd/relations/Relations.relast

src/test/java/org/jastadd/relast/tests/ConstructorsTest.java

src/test/java/org/jastadd/relast/tests/Errors.java