Spurious Velocities for some MPs

[WaveHello]

There's a problem with some of the MP getting spurious velocities. For example, when running FFP impact the MPs on the surface are exploding.

[WaveHello]

Adding a way to scale the velocities of the MP in the MPMDynConvPhase.for file. This is building on the work of Luis and Mohammed where they scaled the velocities of the MP in the adjacent elements to the contact surface. I'm addindg the ability to scale the MPs over a selected area defined using nodes. Defining it using the nodes makes it easier to work with since I'm using a moving mesh then using global coordinates.