re-add the r.mapcalculator momodule (as r.mapcalc.simple) and remove …

…the not working r.mapcalc

python/plugins/processing/algs/grass7/description/r.mapcalc.simple.txt

@@ -0,0 +1,11 @@
+r.mapcalc.simple
+Calculate new raster map from a r.mapcalc expression.
+Raster (r.*)
+ParameterRaster|a|Raster layer A|False
+ParameterRaster|b|Raster layer B|True
+ParameterRaster|c|Raster layer C|True
+ParameterRaster|d|Raster layer D|True
+ParameterRaster|e|Raster layer E|True
+ParameterRaster|f|Raster layer F|True
+ParameterString|expression|Formula|A*2
+OutputRaster|output|Calculated