add simple example plotting a real function

Reals/Grapher.json

+{
+  "svg": "Grapher.svg",
+  "items": [
+    {
+      "id": "fungraph",
+      "attr": "points",
+      "value": "visb_graph"
+    }
+  ],
+  "events": [
+  ]
+}
\ No newline at end of file

Reals/Grapher.mch

+MACHINE Grapher
+DEFINITIONS
+  "LibraryReals.def";
+  "LibraryStrings.def";
+  
+ // generate a SVG points attribute string (e.g. for polygons) from a sequence of pairs of integers:
+ svg_points2str(points) == conc(%i.(i:dom(points)| 
+                                FORMAT_TO_STRING("~w,~w ",[real(i), points(i)])));
+ 
+ // the function to be plotted:                                                          
+ myfunction(x) == 2.0*RSQRT(x)-0.5*RSIN(2.0*x);
+ 
+ mypoints(scale) == %x.(x:1..500| 300.0-scale*myfunction(RDIV(real(x),scale)));
+ 
+ // graph plotted in rectangle (0,0) to (300,300)
+ visb_graph == svg_points2str(mypoints(30.0))
+END
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Reals/Grapher.svg

+<svg height="300" width="500">
+    
+    <polyline id = "fungraph"
+       points="0,0 0,1 10,1 10,0 90,0 90,1 100,1 100,0"
+       stroke="black" 
+       fill="none"
+       opacity="0.70"
+        />
+    <rect x="0" y="0" width="500" height="300" fill="none" stroke="black">
+</svg>