OD user interface for processing measurements

It's currently a pain in the neck to set-up a KF to process measurements. The UI should make it much simpler for set-ups where stations are doing measurements.

After some initial work (in nyx::od::ui), this should be a specific ODProcess structure which allows for the following:

• Switching from an EKF to a CKF a certain number of measurements or using either a function (e.g. covariance below a given threshold)
• Updating the state of the dynamics (cf. the EKF demos in stat_od/two_body.rs)
• Allow for multiple devices to make measurements at the same time (or not)
• Ability to smooth
• Ability to iterate
• Ability to send the estimates and residuals on a channel instead of storing them in a heap-allocated vector
• Covariance mapping