Add alias type definitions for Java

When a spec defines a Model at the top level that is a non-aggretate type (such
as string, number or boolean), it essentially represents an alias for the simple
type. For example, the following spec snippet creates an alias of the boolean
type that for all intents and purposes acts just like a regular boolean.

    definitions:
      JustABoolean:
        type: boolean

This can be modeled in some languages through built-in mechanisms, such as
typedefs in C++. Java, however, just not have a clean way of representing this.

This change introduces an internal mechanism for representing aliases. It
maintains a map in DefaultCodegen that tracks these types of definitions, and
wherever it sees the "JustABoolean" type in the spec, it generates code that
uses the built-in "Boolean" instead.

This functionality currenlty only applies to Java, but could be extended to
other languages later.

The change adds a few examples of this to the fake endpoint spec for testing,
which means all of the samples change as well.

samples/client/petstore/python/test/test_outer_boolean.py

@@ -0,0 +1,42 @@
+# coding: utf-8
+
+"""
+    Swagger Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+    OpenAPI spec version: 1.0.0
+    Contact: apiteam@swagger.io
+    Generated by: https://github.com/swagger-api/swagger-codegen.git
+"""
+
+
+from __future__ import absolute_import
+
+import os
+import sys
+import unittest
+
+import petstore_api
+from petstore_api.rest import ApiException
+from petstore_api.models.outer_boolean import OuterBoolean
+
+
+class TestOuterBoolean(unittest.TestCase):
+    """ OuterBoolean unit test stubs """
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def testOuterBoolean(self):
+        """
+        Test OuterBoolean
+        """
+        model = petstore_api.models.outer_boolean.OuterBoolean()
+
+
+if __name__ == '__main__':
+    unittest.main()

samples/client/petstore/python/test/test_outer_composite.py

@@ -0,0 +1,42 @@
+# coding: utf-8
+
+"""
+    Swagger Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+    OpenAPI spec version: 1.0.0
+    Contact: apiteam@swagger.io
+    Generated by: https://github.com/swagger-api/swagger-codegen.git
+"""
+
+
+from __future__ import absolute_import
+
+import os
+import sys
+import unittest
+
+import petstore_api
+from petstore_api.rest import ApiException
+from petstore_api.models.outer_composite import OuterComposite
+
+
+class TestOuterComposite(unittest.TestCase):
+    """ OuterComposite unit test stubs """
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def testOuterComposite(self):
+        """
+        Test OuterComposite
+        """
+        model = petstore_api.models.outer_composite.OuterComposite()
+
+
+if __name__ == '__main__':
+    unittest.main()

samples/client/petstore/python/test/test_outer_number.py

@@ -0,0 +1,42 @@
+# coding: utf-8
+
+"""
+    Swagger Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+    OpenAPI spec version: 1.0.0
+    Contact: apiteam@swagger.io
+    Generated by: https://github.com/swagger-api/swagger-codegen.git
+"""
+
+
+from __future__ import absolute_import
+
+import os
+import sys
+import unittest
+
+import petstore_api
+from petstore_api.rest import ApiException
+from petstore_api.models.outer_number import OuterNumber
+
+
+class TestOuterNumber(unittest.TestCase):
+    """ OuterNumber unit test stubs """
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def testOuterNumber(self):
+        """
+        Test OuterNumber
+        """
+        model = petstore_api.models.outer_number.OuterNumber()
+
+
+if __name__ == '__main__':
+    unittest.main()

samples/client/petstore/python/test/test_outer_string.py

@@ -0,0 +1,42 @@
+# coding: utf-8
+
+"""
+    Swagger Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+    OpenAPI spec version: 1.0.0
+    Contact: apiteam@swagger.io
+    Generated by: https://github.com/swagger-api/swagger-codegen.git
+"""
+
+
+from __future__ import absolute_import
+
+import os
+import sys
+import unittest
+
+import petstore_api
+from petstore_api.rest import ApiException
+from petstore_api.models.outer_string import OuterString
+
+
+class TestOuterString(unittest.TestCase):
+    """ OuterString unit test stubs """
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def testOuterString(self):
+        """
+        Test OuterString
+        """
+        model = petstore_api.models.outer_string.OuterString()
+
+
+if __name__ == '__main__':
+    unittest.main()