Extrema Detector

Determines local maximums and minimums points in the chart.

Parameters:

• lookback: number of candlesticks to look.
  
• extrema_finder_sensivity: If lower, more extreme points will be found (may over-find).
  

Brief algorithm description:
Computes a Simple Moving Average (length=extrema_finder_sensivity), and searches for its local extremes.
Given some SMA extreme, it looks the previous extrema_finder_sensivity candlesticks to find the highest (or lowest value).

Notes:
Is a lagged indicator: determining if the current candlestick have reach a maximum can be delayed to, at most extrema_finder_sensivity-further candlesticks.

Notes de version:

Fix repaint.
- When a new candlestick is added, the previous plots are deleted (lookback line and min/max labels).