Issue #805: Disable the javac error when a generic subclass of Throwable is declared.
Fix #805 and #1237: test for whether the catch clauses can be handled using multiple Java catch clauses and if not transform using a single catch clause and chained if/else if. Also, in the simple case change the transformation for catch clauses with union types to use a Java 7 union type catch clause, which saves transforming the catch block multiple times.
Issues #805 and #1237: Add tests. Since it's a runtime test, and the trycatch dir contains a module.ceylon I'm splitting out the trycatch tests into their own testcase.
Issues #805 and #1237: Fix up the test .src for the catching a union type, now we're using a Java 7 union catch.