Necessary to avoid travis time out trigger.

Follow the advice of gcc by casting directly with the proposed
CoeffBasedProduct template.
Makes gcc happy.
This patch was initially proposed by Florent Valenza but
with another type.

There is still an issue on ConstraintXd.
This commit *does not* compile is here for book-keeping.

Dev

[Major] Now handle prismatic joint when parsing urdf. Only cartesion X,Y or Z are accepted, unaligned axis bring crash