README: add reference model missing screenshots

A short description is added on top of all screenshots to provide more context
about the purpose of the test diagrams. This description is taken from the
comparison page of the bpmn-miwg-tools site:
  http://bpmn-miwg.github.io/bpmn-miwg-tools/visual-test-result-comparison.html

In addition, fix some typo in text and anchors.

README.md

@@ -9,7 +9,7 @@
 		- [1. Download Test Cases](#user-content-1-download-test-cases)
 		- [2. Test Import, Export and/or Roundtrip of BPMN Models.](#user-content-2-test-import-export-andor-roundtrip-of-bpmn-models)
 		- [3. Submit Your Test Results to BPMN MIWG](#user-content-3-submit-your-test-results-to-bpmn-miwg)
-	- [Detailed Descrition of Test Procedures](#user-content-detailed-descrition-of-test-procedures)
+	- [Detailed Description of Test Procedures](#user-content-detailed-description-of-test-procedures)
 		- [1. BPMN MIWG Import Test Procedure](#user-content-1-bpmn-miwg-import-test-procedure)
 		- [2. BPMN MIWG Export Test Procedure](#user-content-2-bpmn-miwg-export-test-procedure)
 		- [3. BPMN MIWG Roundtrip Test Procedure (BPMN Import and Export combined)](#user-content-3-bpmn-miwg-roundtrip-test-procedure-bpmn-import-and-export-combined)
@@ -47,16 +47,16 @@ Here is how you do it:
 
 ### 1. Download Test Cases
 First download the [latest version of the BPMN Model Interchange Test Suite](https://github.com/bpmn-miwg/bpmn-miwg-test-suite/archive/master.zip) and unpack it.
-TheCe is a directory called `Reference`, which contains the files needed for testing.
+There is a directory called `Reference`, which contains the files needed for testing.
 Next to that, there will be multiple folders with test results of other tools.
 
 ### 2. Test Import, Export and/or Roundtrip of BPMN Models.
-There are [different test procedures](#detailed-descrition-of-test-procedures) that can be performed
+There are [different test procedures](#detailed-description-of-test-procedures) that can be performed
 with the provided reference models depending on the capabilities of the tool.
-You will find explanations of these procedures [below](#detailed-descrition-of-test-procedures).
+You will find explanations of these procedures [below](#detailed-description-of-test-procedures).
 
 ### 3. Submit Your Test Results to BPMN MIWG
-PacCage all result files in a zip file and send it via email to [MIWG@trisotech.com](mailto:MIWG@trisotech.com). Please use the following template for your email:
+Package all result files in a zip file and send it via email to [MIWG@trisotech.com](mailto:MIWG@trisotech.com). Please use the following template for your email:
 
 ```
 Vendor: 
@@ -252,28 +252,88 @@ Verified Reference Models
 -------------------------
 
 ### A.1.0
+_Depict Abstract Elements on a single Sequential Flow_
+
 ![](Reference/A.1.0.png)
+
 ### A.2.0
+_Depict divergence and convergence of flows with unmarked Gateways_
+
 ![](Reference/A.2.0.png)
+
 ### A.2.1
+_Depict divergence and convergence of flows with unmarked Gateways using different type of sequence flows_
+
 ![](Reference/A.2.1.png)
+
 ### A.3.0
+_Depict Exception Flows associated to boundary attachments_
+
 ![](Reference/A.3.0.png)
+
 ### A.4.0
+_Depict graphical elements contained in expanded Sub-Processes, Lanes and Pools_
+
 ![](Reference/A.4.0.png)
+
 ### A.4.1
+_Vertical Modeling Direction_
+
 ![](Reference/A.4.1.png)
+
 ### B.1.0
+_Validate that all the elements prescribed for the Descriptive Conformance Sub-Class in the BPMN 2.0 Specification are present._
+
 ![](Reference/B.1.0.png)
+
 ### B.2.0
+_Validate that all the elements prescribed for the Analytic Conformance Sub-Class in the BPMN 2.0 Specification are present._
+
 ![](Reference/B.2.0.png)
+
 ### C.1.0
+_Executable process containing multiple extension elements and attributes (derived from 2013 Demo in Berlin)_
+
 ![](Reference/C.1.0.png)
+
 ### C.1.1
+_Process from 2015 Execution Demo in Berlin that can be executed in Camunda BPM, OmnyLink and W4 BPMN+_
+
 ![](Reference/C.1.1.png)
+
 ### C.2.0
+_Collaboration from 2015 Diagram Interchange Demo in Berlin_
+
 ![](Reference/C.2.0.png)
+
 ### C.3.0
+_Process with hidden BPMN attributes and elements from 2015 Hidden Attribute Demo in Berlin_
+
 ![](Reference/C.3.0.png)
 
+### C.4.0
+_Process with signal and message events and multiple diagrams, from 2017 Demo in Brussels_
+
+#### C.4.0 diagram 1
+![](Reference/C.4.0.1.png)
+#### C.4.0 diagram 2
+![](Reference/C.4.0.2.png)
+#### C.4.0 diagram 3
+![](Reference/C.4.0.3.png)
+#### C.4.0 diagram 4
+![](Reference/C.4.0.4.png)
+
+### C.5.0
+_Process with data objects and stores and their hidden attributes from 2018 Demo in Seattle_
+#### C.5.0 diagram 1
+![](Reference/C.5.0.1.png)
+#### C.5.0 diagram 2
+![](Reference/C.5.0.2.png)
+
+### C.6.0
+_Process with data input/outputs and event sub-process from 2019 Demo in Amsterdam_
+
+![](Reference/C.6.0.png)
+
+
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