The user wishes to be able to do one of the following to their line chart while allowing it to still export editable to PPT:
* To include the average as a gray line within the chart and color the area under the line in light gray. All the other lines should still be visible (the light gray area under the average line should be in the background/transparent).
* To Include the average as vertical gray bars per category within the chart. All the other lines should still be visible, the average-bar should be in the background/transparent.
* To Include the average as a gray line within the chart. The average should be a different type of line (e.g. thicker, a dotted line or other data markings)