Add ability to select a subset of the data during plotting

[WaveHello]

Currently to plot the df values in GraphFunctions the format is

Frame[xx][::samplespan]

Add a variable so that the format can be

# default data_selection = [0, -1]
data_selection = [num1, num2]

Frame[xx][data_selection[0]:data_selection[1]:samplespan]

samplespan is the spacing selecting between data points samplespan = 1 means go row 0, 1, 2, 3... samplespan = 5 means go row 0, 5, 10

[WaveHello]

Ability added.

[WaveHello]

Add ability to turn off data selection. Add an element to data_selection (third element) that is zero or 1 and acts as a switch for using the value of data_selection or not.