WIP add stewart platform components

MTK with JSCompiler is currently missing a lot of features from modelica that will make it hard to translate this library in a nice way.

Parameters of composite types (in MTK but not in JSCompiler)
Conditional defaults for parameters
Automatic generation of events with when. There is no need to proceed any further with this PR before improvements to the events in MTK are in place.
Simulation-time asserts that throw errors if variables are out of bounds during simulation

JuliaComputing / Multibody.jl