Chart cursor label sometimes doesn't show enough precision

[barnabee]

Description

Expect to be able to read the value from the cursor, but cursor only showing 1 decimal place (see screenshot). Chart axis has two decimals, three (e.g. one more than the chart axis) would probably be appropriate on the cursor.

[johnwalley]

This looks to something that is addressed by #732. The number of decimal places used to format the volume was the same as the number of places used to format prices. These have now been de-coupled by #857.