Corrected some grammar and typo's

Add the the map image file, :kdb:`rautjarvi_map.tif`, as the   -->   the the = double the

:kbd:`exercise_data\forestry\digitizing`              -->       \ = needs double backslashes to show on page

kbd:`KKJ / Finland zone 2` CRS.You will use this  -->               missing space before You

should en up with something similar to this:             -->              en = end

:kbd:`exercise_data\forestry`,                                     -->              \ = needs double backslashes to show on page