Add 2d integrator functionality

[waynemwashuma]

Objective

Adds two dimensional integration methods which are used to move two dimensional entities with velocity and applied forces in both linear and angular displacements through positional integration.
The integrators included are:

• Semi-Implicit Euler intergration through the EulerIntegrator2DPlugin.
• Verlet integration through the VerletIntegrator2DPlugin

Solution

N/A

Showcase

Will add after all physics packages are merged

Migration guide

N/A

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.