Update documentation for modification of mbc and new properties
Update documentation for modification of mbc and new properties

jrl-umi3218/RBDyn,jrl-umi3218/RBDyn,jrl-umi3218/RBDyn,jrl-umi3218/RBDyn,gergondet/RBDyn,gergondet/RBDyn,gergondet/RBDyn,gergondet/RBDyn,gergondet/RBDyn