Added HashCode class.
Added basic hash for HashVisitor class.
Added hashing for known variables with the same hash.
Added literal hashing.
Added if and expression hashing.
Added parse tools so that unit tests can use the ANTLR parser in there tests.
Added unit test HashVisitorIfTest that test the hashing of if blocks.
Added unit test HashVisitorForTest that test the hashing of for blocks.
Added unit test HashVisitorWhileTest that test the hashing of while blocks.
Added unit test HashVisitorSwitchTest that test the hashing of switch blocks.
Added unit test HashVisitorExpressionTest that test the hashing an expression.
Added dependency Hamcrest. Hamcrest is used for JUnit assertThat.
Added unit test HashVisitorNoDuplicatesTest that test if not all the hashes are the same.