[#72] Fixed adding physics to material.

Instead of just adding, possibly existing physics in material name gets
replaced now.
[#33]Material Physics UI

Can now add material physics directly from the Materials tab for
convenience of the user.
Merge pull request #75 from travnick/feature/material_physics_ui

[#33]Material Physics UI
Merge pull request #73 from roidanton/fix/material-physics

[#72] Fixed adding physics to material.
Merge pull request #1 from travnick/develop

Develop