Add a 2D rigid body component

This issue will focus on creating a 1D or 2D rigid body line or box. Said rigid body will initially be constructed in a 2D absolute reference frame / world environment. The component will at least possess the following parameters: s_start, s_end, w (initial angular velocity), a (initial angular acceleration), and m (mass) or rho (density). The parameters s_start and s_end are two points, and a vector will be drawn between them, thereby defining the spatial extents of our rigid body. This "two-point" vector implementation differs from Modelica's implementation of the same component. In the Modelica implementation, one point is used to define the position of the origin of a new frame of reference, and a second point is used to create a vector from the origin of this new frame. Having components possess their own reference frames in this way presents a series of advantages, but for now I will keep my implementation as simple as possible.

No files, tests, or entry points are identified in the issue. Start by locating existing component implementations and their tests, then determine how a 1D or 2D rigid body should represent s_start, s_end, w, a, and mass or density. Done means a working 2D absolute-frame rigid-body component with the stated parameters.