Improving orderBars to also shift single bars by half their width

The behavior of the plugin was inconsistent if only one bar was displayed. In such a case the bar was not shifted. If there was any other uneven number of bars, the center bar was shifted by half its width to be displayed centered around the x value. I added some code to also allow this behavior for single bars.
(Code on lines 61-67 and 228-230)
The remaining changes are a result of me replacing all tabs by spaces to have a consistent usage of spaces for tabs.