Drop builtin command documentation

Drop all GetTerseDocumentation and GetFullDocumentation methods from
commands.  The command documentation is now in Help/command/*.rst files.

Source/cmGetTestPropertyCommand.h

@@ -34,29 +34,6 @@ public:
    */
   virtual const char* GetName() const { return "get_test_property";}
 
-  /**
-   * Succinct documentation.
-   */
-  virtual const char* GetTerseDocumentation() const
-    {
-    return "Get a property of the test.";
-    }
-
-  /**
-   * Longer documentation.
-   */
-  virtual const char* GetFullDocumentation() const
-    {
-    return
-      "  get_test_property(test property VAR)\n"
-      "Get a property from the Test.  The value of the property is "
-      "stored in the variable VAR.  If the property is not found, VAR "
-      "will be set to \"NOTFOUND\". For a list of standard properties "
-      "you can type cmake --help-property-list"
-      "\n"
-      "See also the more general get_property() command.";
-    }
-
   cmTypeMacro(cmGetTestPropertyCommand, cmCommand);
 };