align term matrix sorting in Wilkinson Formula parser.

[AvanishSalunke]

This issues was mentioned before as well in #395

Standard sortrows on the binary terms matrix was sorting 0 before 1 because of this later variables (x3 - 0 0 1) were evaluated before (x1- 1 0 0).

Added negation so that instead of just comparing 0 and 1 it will compare 0 and -1.

MATLAB :

>> formula = 'Y ~ x1 * x2 * x3';
>> mdl = fitlm(t, formula);
>> mdl.Formula.VariableNames

ans =

  1×4 cell array

    {'Y'}    {'x1'}    {'x2'}    {'x3'}

>> mdl.Formula.Terms

ans =

     0     0     0     0
     0     1     0     0
     0     0     1     0
     0     0     0     1
     0     1     1     0
     0     1     0     1
     0     0     1     1
     0     1     1     1

OCTAVE (before) :

octave:5>  eq = parseWilkinsonFormula ('Y ~ x1 * x2 * x3', 'matrix');
octave:6> eq.VariableNames
ans =
  1x4 cell array

    {'Y'}    {'x1'}    {'x2'}    {'x3'}    

octave:7> eq.Terms
ans =

   0   0   0   0
   0   0   0   1
   0   0   1   0
   0   1   0   0
   0   0   1   1
   0   1   0   1
   0   1   1   0
   0   1   1   1

OCTAVE (after) :

octave:5> eq = parseWilkinsonFormula ('Y ~ x1 * x2 * x3', 'matrix');
octave:6> eq.VariableNames
ans =
  1x4 cell array

    {'Y'}    {'x1'}    {'x2'}    {'x3'}    

octave:7> eq.Terms
ans =

   0   0   0   0
   0   1   0   0
   0   0   1   0
   0   0   0   1
   0   1   1   0
   0   1   0   1
   0   0   1   1
   0   1   1   1