Changing default Jack arguments.

This change sets Jack default arguments to enable some of lambda
optimizations, namely: lambda grouping in scope of a single package
and using singletin lambda objects for stateless lambdas.

Test: tested manually

Change-Id: Id2d0c37e3462f1e3137cfef2684cf6e74df6089b
diff --git a/core/jack-default.args b/core/jack-default.args
index 0232301..433bc53 100644
--- a/core/jack-default.args
+++ b/core/jack-default.args
@@ -5,3 +5,5 @@
 -D jack.reporter.level.file=error=--,warning=-
 --verbose error
 -D jack.jayce.cache=false
+-D jack.lambda.grouping-scope=package
+-D jack.lambda.simplify-stateless=true