Added file "Test-execution.md" with information on the TDL execution

feature.

Test-execution.md

+## Test execution
+
+The TOP tool supports execution of complete TDL models. 
+
+The model is translated to java code and the TOP tool provides components to interface a
+test with the SUT.
+
+
+
+## Test result analysis
+
+The TDL execution feature provides a Report component that enables logging of events which
+is the basis for test result analysis. It allows events during a test execution to be logged 
+and hence these event traces may be used to check the result of a test.
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