Better EMR coverage and boto3 request/response handling

This revision includes:

- A handler for requests for which content-type is JSON (from boto3).

- A decorator (generate_boto3_response) to convert XML responses to
  JSON (for boto3). This way, existing response templates for boto can
  be shared for generating boto3 response.

- Utility class/functions to use botocore's service specification data
  (accessible under botocore.data) for type casting, from query
  parameters to Python objects and XML to JSON.

- Updates to response handlers/models to cover more EMR end points and
  mockable parameters

tests/test_core/test_responses.py

@@ -0,0 +1,73 @@
+from __future__ import unicode_literals
+
+import sure  # noqa
+
+from moto.core.responses import AWSServiceSpec
+from moto.core.responses import flatten_json_request_body
+
+
+def test_flatten_json_request_body():
+    spec = AWSServiceSpec('data/emr/2009-03-31/service-2.json').input_spec('RunJobFlow')
+
+    body = {
+        'Name': 'cluster',
+        'Instances': {
+            'Ec2KeyName': 'ec2key',
+            'InstanceGroups': [
+                {'InstanceRole': 'MASTER',
+                 'InstanceType': 'm1.small'},
+                {'InstanceRole': 'CORE',
+                 'InstanceType': 'm1.medium'},
+            ],
+            'Placement': {'AvailabilityZone': 'us-east-1'},
+        },
+        'Steps': [
+            {'HadoopJarStep': {
+                'Properties': [
+                    {'Key': 'k1', 'Value': 'v1'},
+                    {'Key': 'k2', 'Value': 'v2'}
+                ],
+                'Args': ['arg1', 'arg2']}},
+        ],
+        'Configurations': [
+            {'Classification': 'class',
+             'Properties': {'propkey1': 'propkey1',
+                            'propkey2': 'propkey2'}},
+            {'Classification': 'anotherclass',
+             'Properties': {'propkey3': 'propkey3'}},
+        ]
+    }
+
+    flat = flatten_json_request_body('', body, spec)
+    flat['Name'].should.equal(body['Name'])
+    flat['Instances.Ec2KeyName'].should.equal(body['Instances']['Ec2KeyName'])
+    for idx in range(2):
+        flat['Instances.InstanceGroups.member.' + str(idx + 1) + '.InstanceRole'].should.equal(body['Instances']['InstanceGroups'][idx]['InstanceRole'])
+        flat['Instances.InstanceGroups.member.' + str(idx + 1) + '.InstanceType'].should.equal(body['Instances']['InstanceGroups'][idx]['InstanceType'])
+    flat['Instances.Placement.AvailabilityZone'].should.equal(body['Instances']['Placement']['AvailabilityZone'])
+
+    for idx in range(1):
+        prefix = 'Steps.member.' + str(idx + 1) + '.HadoopJarStep'
+        step = body['Steps'][idx]['HadoopJarStep']
+        i = 0
+        while prefix + '.Properties.member.' + str(i + 1) + '.Key' in flat:
+            flat[prefix + '.Properties.member.' + str(i + 1) + '.Key'].should.equal(step['Properties'][i]['Key'])
+            flat[prefix + '.Properties.member.' + str(i + 1) + '.Value'].should.equal(step['Properties'][i]['Value'])
+            i += 1
+        i = 0
+        while prefix + '.Args.member.' + str(i + 1) in flat:
+            flat[prefix + '.Args.member.' + str(i + 1)].should.equal(step['Args'][i])
+            i += 1
+
+    for idx in range(2):
+        flat['Configurations.member.' + str(idx + 1) + '.Classification'].should.equal(body['Configurations'][idx]['Classification'])
+
+        props = {}
+        i = 1
+        keyfmt = 'Configurations.member.{0}.Properties.entry.{1}'
+        key = keyfmt.format(idx + 1, i)
+        while key + '.key' in flat:
+            props[flat[key + '.key']] = flat[key + '.value']
+            i += 1
+            key = keyfmt.format(idx + 1, i)
+        props.should.equal(body['Configurations'][idx]['Properties'])