documentation updates and test_containers target

Change-Id: Idea1a3de9dd23d57db3eefd072d650e7db2e0036
diff --git a/common/Makefile b/common/Makefile
index 6a54b74..79e69b6 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -141,6 +141,8 @@
 
 local_containers: prereqs xos_download update_certs xos_base_c xos_devel_c
 
+test_containers: local_containers xos_test_c
+
 update_certs:
 	echo "" > $(XOS_DIR)/containers/xos/local_certs.crt
 	for CRT in $$(ls /usr/local/share/ca-certificates/*) ; do \
@@ -158,6 +160,7 @@
 xos_test_c:
 	cd $(XOS_DIR)/containers/xos; make test
 
+
 # utilties/convenience targets
 cleanup: stop rm
 	$(CONFIG_DIR)/cleanup.sh