Add min_number parameter to segmentize

I am working on a neural network which operates on polylines with variable number of vertices. To fit each polyline into the ANN the simplify method works well to reduce the number of vertices of long polylines. However to *increase* the number of vertices for short polylines, I am out of luck (currently I just fill the matrix with zeros but I suspect that may limiting the sensitivity of the model). I am thinking that `segmentize` could work similar to `simplify` where you either pass in `max_distance` or `min_number` (but not both), and if you pass in `min_number` a simple algorithm of inserting a redundant vertex in the center of the longest line iteratively until the `min_number` is reached.