Parse::Gnaw::LinkedListLetterDimensions2 - Create a Parsable linked list of Parse::Gnaw::Letter objects, with 4 axis of dimension. This would be equivalent to a 2-dimensional block of text, equivalent to somthing like:
a-b-c |X|X| d-e-f |X|X| g-h-i
return a hash containing the default values for constructor arguments. this gets overloaded by derived classes so base constructor always does the right thing.
The variable names reflect the physical position of hte letters
The axis interconnect the letters as follows:
0 => horizontally 1 => vertically 2 => diagonal upper left to lower right 3 => diagonal upper right ot lower left
Assume that axis  is already connected. We need to connect axis 1,2,3