VolumeColumn updates:
    - changed some variable/attribute names
    - added ability to move columns to the bottom layer
    - updated to use unique colors from other priceUp/priceDown indicators.
	modified:   ../../build/gallery-charts-stockindicators/gallery-charts-stockindicators-coverage.js
	modified:   ../../build/gallery-charts-stockindicators/gallery-charts-stockindicators-debug.js
	modified:   ../../build/gallery-charts-stockindicators/gallery-charts-stockindicators-min.js
	modified:   ../../build/gallery-charts-stockindicators/gallery-charts-stockindicators.js
Add some tests to ensure the right paths are used for each column.