* added inner Modelica.Mechanics.MultiBody.World as required by Modelica.Mechanics.MultiBody.Visualizers.Advanced.Arrow and Modelica.Mechanics.MultiBody.Visualizers.Advanced.DoubleArrow
 * The state variable PlanarMechanics.Joints.Prismatic.s is of type Modelica.SIunits.Distance which means that the minimum length is zero. This is not suitable for simulation which negative elongations. See also [Mo#446](https://trac.modelica.org/Modelica/ticket/446) where there was the same problem.
 * Did some cosmetics.
Merge pull request #14 from tbeu/master

Issues with SI.Distance and MB.World
Fixed typo
Fixed typo
Fixed typo
Added s.start and v.start to Initialization group

Thus it is consistent with Revolute
Move position of param animation

Make it consistent with Prismatic
Merge pull request #17 from tbeu/patch-2

Fixed typos
Merge pull request #18 from tbeu/patch-3

Added s.start and v.start to Initialization group
Merge pull request #19 from tbeu/patch-4

Move position of param animation