8.0 wmsqtyavailprec jco

We want a consistent use of rounding and precision of the product quantities.  The rounding is done according to the rounding of the default product UoM.  Behind the scenes we always convert the quantity of the moves and pack operations to the quantity in default UoM and apply its rounding there before doing any further operations.  Float_compare are done everywhere in stock operations.  @odony 
Commented code is for clarity and float_compare >= 0, not > 0