### Euler Implicit Solver

Description
The EulerImplicitSolver can be used to solve ODE systems of first or second order, using the Euler implicit integration scheme. The step size of the discretization corresponds to the timeStep of SOFA.
At each step of the scheme, the linear equation systems obtained have to be solved by an auxiliary component, the CGLinearSolver, which can be of different kinds (conjugated gradient, ...).
Key points
Different simulations are proposed:

- Green: reference deformation.
- Yellow: Mechanical system using springs along edges.
- Light blue: Mechanical system using tetrahedron finite elements.
- Blue: Same system as before but using a first order integration scheme.
- Red: Mechanical system with tetrahedron finite linear elements.

Results