[python-client] Add model default values (#1776)

* Adds two models to the v2.0 spec, uses examples as defaults in python client

* Adds array default and type_holder_default and type_holder_example tests

* Re-generated python security client with ./bin/security/python-petstore.sh

* Changes comment text, rebased master

* Updates client + server samples

* Adds missing samples updates

* Changes python client to look for true or false with booleans in toDefaultValue

* Changes boolean casting to use Boolean.valueOf

* Adds deserialization fix for python tests

* Changes Mock to namedtuple in python deserialization tests

* Actually remove unittest.mock

samples/client/petstore/java/google-api-client/docs/TypeHolderDefault.md

@@ -0,0 +1,14 @@
+
+# TypeHolderDefault
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**stringItem** | **String** |  | 
+**numberItem** | [**BigDecimal**](BigDecimal.md) |  | 
+**integerItem** | **Integer** |  | 
+**boolItem** | **Boolean** |  | 
+**arrayItem** | **List<Integer>** |  | 
+
+
+

samples/client/petstore/java/google-api-client/docs/TypeHolderExample.md

@@ -0,0 +1,14 @@
+
+# TypeHolderExample
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**stringItem** | **String** |  | 
+**numberItem** | [**BigDecimal**](BigDecimal.md) |  | 
+**integerItem** | **Integer** |  | 
+**boolItem** | **Boolean** |  | 
+**arrayItem** | **List<Integer>** |  | 
+
+
+