completeCompilationUnit: Add try/catch/finally

For #39.
completeCompilationUnit: Add assertion, conditions

For #39.
CeylonExpressionTransformer: Fix MemberMeta
completeCompilationUnit: Add metas

For #39.
CeylonExpressionTransformer: Improve decs

If the qualifier is ‘null’, we use the shorter, positional arguments
form.
completeCompilationUnit: Add decs

For #39.