Only show patched conics if the frame makes sense

[eggrobin]

Progress on #3441.

Displaying patched conics is a way to visualize the discrepancy between Princpia’s modeling and the approximations used by stock (chiefly patched conics, as in Figure 1, but also impulsive manœuvres, as in Figure 2).

Figure 1	Figure 2

However, enabling all patched conics leads to misleading display, as some conics, such as the trajectories of faraway planets, are displayed in a different reference frame (Figure 3). Depending on the choice of reference frame, all conics can be inappropriate, leading to a confusing mess (Figure 4).

Figure 3	Figure 4

This change avoids drawing most of the inappropriate conics. Further work is needed to avoid drawing those parts of a flight plan that are drawn as orbits about a parent of the current main body, as in Figure 5, which shows a planned conic in HCI but everything else in KCI.

Figure 5