6 Link Inertias definable (instead of only 3)

[Robert Katzschmann]

the dynamics engine needs to be enhanced to the general case of taking 6 inertia parameters instead of 3.

Currently definable: Ixx, Iyy, Izz Missing: Ixy, Ixz, Iyz

[Samir Menon]

Added as of : a6760c9b77a771d0000ecef3cdecb48727f34c9d

In the config file, two options are possible: Option 1 : {Ixx, Iyy, Izz} Option 2 : {Ixx, Iyy, Izz, Ixy, Ixz, Iyz}