Missing values display when verbose activated

[eragot]

Hi,

Should be good to display the umbrella chart when a parsing error occur in order to see which line in the chart causing problem.
Currently only the line number is display with a message but impossible to know which directive in the chart is wrong.

Thanks a lot
BR

[pamiel]

While this feature is now available for Spray v3.x since #45, it has been "lost" when moving to Spray v4 => keeping the issue open.

[cvila84]

Also fixed in v4