Enums
Enum for SE(2) element. SE(2) element can be expressed in three forms,i.e. in group, in algebra, and in vector.
Traits
a trait for transforming the SE(2) element from one form to another
Functions
SE(2) mapping vec3 to group
SE(2) mapping group to vec3
combine vector2 and scalar (ρ θ) into one vector3 (τ)
decombine a vector3 τ into vector2 and scalar, (ρ θ)
SE(2) mapping algebra to group
SE(2) mapping vector to algebra
TODO ： CHECK for left jac and right jac conversion
SE(2) get right jacobian matrix
SE(2) mapping group to algebra
SE(2) mapping algebra to vector