Things we will want to simplify:
  
   2.y.3 -> 6.y
   y.x.3 + x^2 +1 -> x^2 + 3*x*y + 1
  Zeroes and ones
   x + 0 -> x
   1*x -> x
   x^1 -> x
   x^0 -> 1
  Simplify fractions
   (x^2+5.x+6)/(x+2) -> x+3
  Polynomials
   (x+1)^2-x^2 -> 2*x+1
  Fractions
   (2*x)/(x^2-1) - 1/(x-1) -> 1/(x+1)
  Functional identities
    ln(2x) - ln(x) -> ln(2)
    y*sin^2(x) + y*cos^2(x) -> y
  
  Note : The simplification process can be interrupted! -> It probably browses a graph