MBD: added mass scaled with 2D width and free_x/free_r (#725)
MBD: added mass scaled with 2D width and free_x/free_r (#725)

* MBD: AM matrix off-diagonal terms scaled with free_x/r

* MBD: added mass matrix scaled with width (2D)

erdc/proteus,erdc/proteus,erdc/proteus,erdc/proteus