Correct spelling errors [ci skip]

  connot    -> cannot
  verticies -> vertices

doc/grids/dgf/examplegrid1c.dgf

 DGF
-Vertex        % the verticies of the grid
+Vertex        % the vertices of the grid
 -1   -1       % vertex 0
 -0.2 -1       % vertex 1
  1   -1       % vertex 2
@@ -9,7 +9,7 @@ Vertex        % the verticies of the grid
 0.2  -0.2     % vertex 6
 #
 CUBE            % a cube grid
-0 1 5 6         % cube 0, verticies 0,1,5,6
+0 1 5 6         % cube 0, vertices 0,1,5,6
 1 2 6 3         % cube 1
 6 3 5 4         % cube 2
 #

doc/grids/dgf/examplegrid1gen.dgf

@@ -7,7 +7,7 @@ display 0
 %path $HOME/bin  % path to Triangle
 
 #
-Vertex        % the verticies of the grid
+Vertex        % the vertices of the grid
 -1   -1       % vertex 0
 -0.2 -1       % vertex 1
  1   -1       % vertex 2

doc/grids/dgf/examplegrid1s.dgf

 DGF
-Vertex        % the verticies of the grid
+Vertex        % the vertices of the grid
 -1   -1       % vertex 0
 -0.2 -1       % vertex 1
  1   -1       % vertex 2
@@ -9,7 +9,7 @@ Vertex        % the verticies of the grid
 0.2  -0.2     % vertex 6
 #
 SIMPLEX       % a simplex grid
-0 1 5         % triangle 0, verticies 0,1,5
+0 1 5         % triangle 0, vertices 0,1,5
 1 3 6         % triangle 1
 1 2 3         % triangle 2
 6 3 4         % triangle 3

dune/grid/io/file/dgfparser/dgfparser.cc

@@ -52,7 +52,7 @@ namespace Dune
     {
       out << "Step 1 finished: " << std::endl;
       out << "                 " << dimw << "d" << std::endl;
-      out << "                 " << nofvtx << " verticies" << std::endl;
+      out << "                 " << nofvtx << " vertices" << std::endl;
       out << "                 " << nofel << " elements" << std::endl;
     }
 
@@ -651,7 +651,7 @@ namespace Dune
                    << dimw << " dimensions!");
       } else if (dimw==-1) {
         DUNE_THROW(DGFException,
-                   "SimplexGen: connot determine dimension of grid," <<
+                   "SimplexGen: cannot determine dimension of grid," <<
                    " include parameter DIMENSION in the "
                                                                      << "Simplexgeneration-Block");
       }