New Axis scale type: Discrete to support skipping weekend and holidays in financial plots

ORG-12946

Use discrete as plot scale type to skip weekend when plotting

When plotting financial graph where there is no trading on weekends and holidays, there used to be a gap in axis.

But now in Origin 2016, by using Discrete scale type, there will be no such gaps and the data will look more cotinuous.

This is the default setting for all plot types under Plot: Stock: menu.

If Discrete is set as scale type, no gap between candle sticks.

Old way: Axis Scale is Linear, there are gaps on weekend and holidays.

Basically if Discrete is set as scale type, missing data is not plotted and continuity preserves.

Add a Line option under Plot: Stock menu and the toolbar
If make line plot with Plot:Stock:Plot, x axis scale type is set to discrete by default.