Minor formatting corrections

Related open issue SAP-samples#9:
```
Following points are missing from the Exercise 2:
Title

Exercise 2: Adapt the generated code
Introduction and Hyperlink and bulletpoints for the chapters
Chapters

Exercise 2.X ... is missing
Hyperlink to top of the page
Ending

Summary and Hyperlink to the next Exercise
```

rap6xx/rap620/exercises/ex2/README.md

@@ -1,19 +1,20 @@
 # TOC
 [Home](../../readme.md#exercises)
-# Adapt the generated code
-
+# Exercise 2: Adapt the generated code
+## Introduction
 In this exercise we will perform changes to the generated code so that our application becomes usable. 
 
-- _Projection view_:  
+- [_Projection view_](#projection-view):  
 Here we will add value help definitions for the currency code and quantity units.
 
-- _Metadata extension file_:  
+- [_Metadata extension file_](#metadata-extension-file):  
 Since we use built-in ABAP data types rather than data elements we have to add UI annotations to provide a label for the columns in the list view and the fields in the object page.
 
-- _Behavior Definition_ and _Behavior Implementation_:  
+- [_Behavior Definition_](#behavior-definition) and [_Behavior Implementation_](#behavior-implementation):  
 Here we will make the semantic key field **InventoryID** _read_only_ and we will add a determination to the behavior definition and implement the same in the behavior implementation clas so that the semantic key field **InventoryID** will be filled automatically.
 
 ## Projection view
+[^Top of page](#toc)
 
 In the source code of the projection view ````ZRAP620_C_INVENTORYTP_### ```` we will add two value help definitions for the fields ````QuantityUnit```` and ````CurrencyCode````. 
 
@@ -58,6 +59,7 @@ define root view entity ZRAP620_C_INVENTORYTP_###
 </details>
 
 ## Metadata extension file
+[^Top of page](#toc)
 
 Open the metadata extension file ````ZRAP620_C_INVENTORYTP_### ````. Replace the complete source code with the following code snippet and use search and replace to change the placeholder ````###````.
 
@@ -207,6 +209,7 @@ annotate view ZRAP620_C_INVENTORYTP_### with
 </details>
 
 ## Behavior definition
+[^Top of page](#toc)
 
 Open the behavior defintion ````ZRAP620_R_INVENTORYTP_### ```` and add the field **InventoryID** to the list of fields that are marked as readonly and add a determination **CalculateInventoryID** for the field **InventoryID**.
 
@@ -262,6 +265,7 @@ determination CalculateInventoryID on save { create; }
 </details>
 
 ## Behavior implementation
+[^Top of page](#toc)
 
 The behavior implementation class ````ZRAP620_BP_INVENTORYTP_###```` is automatically opened with the tab **Local Types** for the local handler class ````lcl_handler```` .
 The quick fix has added a method ````CalculateInventoryID```` with an (empty) implementation for the determination that shall calculate the semantic key InventoryID. 
@@ -323,7 +327,8 @@ ENDMETHOD.
 </details>
 
 # Test your changes
-
+[^Top of page](#toc)
+
 After having performed all the changes mentioned above we can use the SAP Fiori Elements preview in ADT to test our updated implementation.   
 
 <details>