[Feature Request] Show remaining filament in ongoing print

[VanessaE]

It would be a good idea to have Pronterface show how much filament is still to be used in the current print. This would be especially useful if your spool is running low; while Pronterface has no way to know how much is on the spool, it would enable the user to quickly guess if there's enough filament to finish the print unattended, based on what Pronterface says still needs to be laid down.

The status bar could be altered to put the remaining and total filament right after the time (rounded to the nearest, say, 0.1 m), so that it reads something like:

Printing: 34.67% | Line # 94057 of 271292 lines | Est: 0:54:47 of 1:36:19 remaining (5.0 m of 8.3 m) | Z: 4.400 mm

We chatted about this in IRC a while back, and I only just now remembered to file a proper issue.