Don't render draft, maxspeed… limits on waterways

[pyrog]

Theses keys could be used by :

• GPS navigation systems to display an alarm when speed is to high.
• routing software to compute the duration of the trip, or avoiding channels when deep is to low…

Render only nodes with waterway:sign tag.

Code :

• draft labels.mss lines 546
• maxspeed labels.mss lines 569