As an enhancement to https://github.com/localstack/localstack/pull/1194

It would be really helpful to send the Lambda name, either as data, a header, or as part of the URL.

At code location: https://github.com/localstack/localstack/blob/03c6f4bf250edd18eb818ed65090f508636b0bff/localstack/services/awslambda/lambda_api.py#L696

I can likely open a PR to handle this given some feedback on the feature and potential design.

Right now all I see is the following (using `npx http-echo-server`):
```
[socket#8] event: data
--> POST / HTTP/1.1
--> Host: 192.168.1.x:3000
--> User-Agent: python-requests/2.22.0
--> Accept-Encoding: gzip, deflate
--> Accept: */*
--> Connection: keep-alive
--> Content-Length: 9
--> Content-Type: application/x-www-form-urlencoded
-->
-->
[socket#8] event: data
--> Name=test
```
@classmethod
    def setUpClass(cls):
        cls.lambda_client = aws_stack.connect_to_service('lambda')
        cls.s3_client = aws_stack.connect_to_service('s3')
        cls.sns_client = aws_stack.connect_to_service('sns')
        Util.create_function(TEST_LAMBDA_PYTHON, TEST_LAMBDA_NAME_PY,
                             runtime=LAMBDA_RUNTIME_PYTHON27, libs=TEST_LAMBDA_LIBS)
    @classmethod
    def tearDownClass(cls):
        testutil.delete_lambda_function(TEST_LAMBDA_NAME_PY)
    def test_invocation_type_not_set(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_PY, Payload=b'{}')
        result_data = json.loads(result['Payload'].read())
        self.assertEqual(result['StatusCode'], 200)
        self.assertEqual(result_data['event'], json.loads('{}'))
    def test_invocation_type_request_response(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_PY,
            Payload=b'{}', InvocationType='RequestResponse'
        )
        result_data = result['Payload'].read()
        result_data = json.loads(to_str(result_data))
        self.assertEqual(result['StatusCode'], 200)
        self.assertIsInstance(result_data, dict)
    def test_invocation_type_event(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_PY,
            Payload=b'{}', InvocationType='Event')
        self.assertEqual(result['StatusCode'], 202)