Add C to integration result, change integral node to support range instead of iterations, implement u-substitution and quadratic denominator integral, integration of abs(x), sgn(x) and ln(abs(x))^2

Add C to integration result, change integral node to support range instead of iterations, implement u-substitution and quadratic denominator integral, integration of abs(x), sgn(x) and ln(abs(x))^2 #964