r.mapcalc.simple: screenshot added (#188)

- GUI screenshot added to r.mapcalc.simple
- fix typo in r.sunhours manual (fixes https://trac.osgeo.org/grass/ticket/3935)

raster/r.sunhours/r.sunhours.html

@@ -22,9 +22,9 @@ If a <em>sunhour</em> output map is specified, the module calculates
 sunshine hours for the given day. This option requires both Greenwhich 
 standard time and the use of the SOLPOS algorithm by NREL.
 
-<h2>NOTESS</h2>
+<h2>NOTES</h2>
 
-To consider also cast shadow effects of the terrain, <em>r.sun</em> is
+To consider also cast shadow effects of the terrain, <em>r.sun</em> has
 to be used.
 
 <h2>EXAMPLES</h2>

scripts/r.mapcalc.simple/r.mapcalc.simple.html

@@ -78,6 +78,11 @@ r.mapcalc.simple expression="A + B + C" a=zeros b=ones c=twos output=result1
 r.mapcalc.simple expression="(A * B) / 2 + 3 * C" a=zeros b=ones c=twos output=result2
 </pre></div>
 
+<div align="center" style="margin: 10px">
+<img src="r_mapcalc_simple.png" width="594px" height="495px"><br>
+<i>Figure: r.mapcalc.simple graphical user interface</i>
+</div>
+
 
 <h3>Example expressions</h3>