Cleanup `ChMaterial.h` and `ChVsualization.h`

- remove using directives
- use cont references where appropriate
- reformatting (untabify)
Place all classes in `particlefactory` in the namespace `chrono::particlefactory`

Without this, the implementation depended implicitly on the `chrono` namespace being available through a using declaration in one of the included headers.
Moreover, it is appropriate for all Chrono classes to be defined within the main `chrono` namespace.
Fix issues related to the `chrono` namespace not available anymore through some included header.

NOTE: this is a fix consistent with current implementation of the rest of the irrlicht_interface. A better fix is to define all classes in this module within the main `chrono` namespace.