Add rule group_name parameter whose value can reference containing group name.

cloud/ec2_group

@@ -87,7 +87,10 @@ EXAMPLES = '''
       - proto: udp
         from_port: 10051
         to_port: 10051
-        group_id: abcdef
+        group_id: sg-12345678
+      - proto: all
+        # the containing group name may be specified here
+        group_name: example
 '''
 
 try:
@@ -152,6 +155,7 @@ def main():
     groups = {}
     for curGroup in ec2.get_all_security_groups():
         groups[curGroup.id] = curGroup
+        groups[curGroup.name] = curGroup
 
         if curGroup.name == name and curGroup.vpc_id == vpc_id:
             group = curGroup
@@ -203,11 +207,22 @@ def main():
         if rules:
             for rule in rules:
                 group_id = None
+                group_name = None
                 ip = None
                 if 'group_id' in rule and 'cidr_ip' in rule:
                     module.fail_json(msg="Specify group_id OR cidr_ip, not both")
+                elif 'group_id' in rule and 'group_name' in rule:
+                    module.fail_json(msg="Specify group_id OR group_name, not both")
                 elif 'group_id' in rule:
                     group_id = rule['group_id']
+                elif 'group_name' in rule:
+                    group_name = rule['group_name']
+                    if group_name in groups:
+                        group_id = groups[group_name].id
+                    elif group_name == name:
+                        group_id = group.id
+                        groups[group_id] = group
+                        groups[group_name] = group
                 elif 'cidr_ip' in rule:
                     ip = rule['cidr_ip']