Implement multitree lunch

Test: (cd build/make/orchestrator/core ; ./test_lunch.py)
Change-Id: I4ba36a79abd13c42b986e3ba0d6d599c1cc73cb0
diff --git a/orchestrator/multitree_combos/test.mcombo b/orchestrator/multitree_combos/test.mcombo
new file mode 100644
index 0000000..3ad0717
--- /dev/null
+++ b/orchestrator/multitree_combos/test.mcombo
@@ -0,0 +1,16 @@
+{
+    "lunchable": true,
+    "system": {
+        "tree": "inner_tree_system",
+        "product": "system_lunch_product"
+    },
+    "vendor": {
+        "tree": "inner_tree_vendor",
+        "product": "vendor_lunch_product"
+    },
+    "modules": {
+        "com.android.something": {
+            "tree": "inner_tree_module"
+        }
+    }
+}