Add EulerXYZJoint.
Add skel formation description file.
Change the name DART format to skel format.
Add EulerXYZJoint.
Fix code style.
Add mass aggregation method for forward dynamics.
Add automatic moment of inertia calculation.
Add more test skel files.
Change .gitignore
Change app.
Merge branch 'origin/refactoring'

Conflicts:
	src/math/LieGroup.cpp