[Feature] Quadratic regularizer with nonzero baseline

[andgoldschmidt]

Is your feature request related to a problem? Please describe. Sometimes we might want to keep controls or trajectories close to some baseline. Currently, $||a||_R$ is allowed, but the new feature should allow for $||a - a_0||_R$.

Describe the solution you'd like The QuadraticRegularizer objectives can be modified with an optional argument for the new feature. The objective function, gradient, and hessian can be modified to account for the shifted baseline.

[andgoldschmidt]

This has been implemented on a feature branch, but needs to be tested and merged into main.

Some problem templates may want to allow access to this feature via a keyword argument.