Hurst Constant Envelope

This script follows the fundamentals described in J.M. Hurst works.
Constant Envelope is updated version of EMA with its 2 copies drawn with nominal distance from the base.
That make a constant width channels, unlike the standard envelope using the % concept.
Its width is not changed at different price levels.

Release Notes:

the Moving average last value is set up to be a half of wave length from the last bar on the chart
so is the default offset

changed shift to width

Release Notes:

Added second harmonic envelope, with span 2x basic

Release Notes:

Previous version had a mistake in theory, now
The second harmonic is now envelope with half span of the basic. Just as defined in "The Profit Magic Of Transaction Timing"