[markdown] Fix broken links when generating markdown (#5569)

* [markdown] Fix broken links when generating markdown

The `api.mustache` file generates links to the markdown model files.
These links were previously brokeen.

Additionally, the defaultPackage for markdown is "/Models", so this
looked pretty in the heading for model files. So this prefix has been
stripped from the header in `model.mustache`.

* Re-generate Petstore samples for markdown

samples/documentation/markdown/Apis/PetApi.md

@@ -24,7 +24,7 @@ Add a new pet to the store
 
 Name | Type | Description  | Notes
 ------------- | ------------- | ------------- | -------------
- **body** | [**Pet**](/Models/Pet.md)| Pet object that needs to be added to the store |
+ **body** | [**Pet**](..//Models/Pet.md)| Pet object that needs to be added to the store |
 
 ### Return type
 
@@ -77,11 +77,11 @@ Finds Pets by status
 
 Name | Type | Description  | Notes
 ------------- | ------------- | ------------- | -------------
- **status** | [**List**](/Models/String.md)| Status values that need to be considered for filter | [default to null] [enum: available, pending, sold]
+ **status** | [**List**](..//Models/String.md)| Status values that need to be considered for filter | [default to null] [enum: available, pending, sold]
 
 ### Return type
 
-[**List**](/Models/Pet.md)
+[**List**](..//Models/Pet.md)
 
 ### Authorization
 
@@ -104,11 +104,11 @@ Finds Pets by tags
 
 Name | Type | Description  | Notes
 ------------- | ------------- | ------------- | -------------
- **tags** | [**List**](/Models/String.md)| Tags to filter by | [default to null]
+ **tags** | [**List**](..//Models/String.md)| Tags to filter by | [default to null]
 
 ### Return type
 
-[**List**](/Models/Pet.md)
+[**List**](..//Models/Pet.md)
 
 ### Authorization
 
@@ -135,7 +135,7 @@ Name | Type | Description  | Notes
 
 ### Return type
 
-[**Pet**](/Models/Pet.md)
+[**Pet**](..//Models/Pet.md)
 
 ### Authorization
 
@@ -156,7 +156,7 @@ Update an existing pet
 
 Name | Type | Description  | Notes
 ------------- | ------------- | ------------- | -------------
- **body** | [**Pet**](/Models/Pet.md)| Pet object that needs to be added to the store |
+ **body** | [**Pet**](..//Models/Pet.md)| Pet object that needs to be added to the store |
 
 ### Return type
 
@@ -214,7 +214,7 @@ Name | Type | Description  | Notes
 
 ### Return type
 
-[**ApiResponse**](/Models/ApiResponse.md)
+[**ApiResponse**](..//Models/ApiResponse.md)
 
 ### Authorization
 

samples/documentation/markdown/Models/ApiResponse.md

@@ -1,4 +1,4 @@
-# ./Models.ApiResponse
+# ApiResponse
 ## Properties
 
 Name | Type | Description | Notes

samples/documentation/markdown/Models/Category.md

@@ -1,4 +1,4 @@
-# ./Models.Category
+# Category
 ## Properties
 
 Name | Type | Description | Notes

samples/documentation/markdown/Models/Order.md

@@ -1,4 +1,4 @@
-# ./Models.Order
+# Order
 ## Properties
 
 Name | Type | Description | Notes

samples/documentation/markdown/Models/Pet.md

@@ -1,4 +1,4 @@
-# ./Models.Pet
+# Pet
 ## Properties
 
 Name | Type | Description | Notes

samples/documentation/markdown/Models/Tag.md

@@ -1,4 +1,4 @@
-# ./Models.Tag
+# Tag
 ## Properties
 
 Name | Type | Description | Notes

samples/documentation/markdown/Models/User.md

@@ -1,4 +1,4 @@
-# ./Models.User
+# User
 ## Properties
 
 Name | Type | Description | Notes

samples/documentation/markdown/README.md

@@ -32,12 +32,12 @@ Class | Method | HTTP request | Description
 <a name="documentation-for-models"></a>
 ## Documentation for Models
 
- - [/Models.ApiResponse](Models/ApiResponse.md)
- - [/Models.Category](Models/Category.md)
- - [/Models.Order](Models/Order.md)
- - [/Models.Pet](Models/Pet.md)
- - [/Models.Tag](Models/Tag.md)
- - [/Models.User](Models/User.md)
+ - [ApiResponse](.//Models/ApiResponse.md)
+ - [Category](.//Models/Category.md)
+ - [Order](.//Models/Order.md)
+ - [Pet](.//Models/Pet.md)
+ - [Tag](.//Models/Tag.md)
+ - [User](.//Models/User.md)
 
 
 <a name="documentation-for-authorization"></a>