Allow inertia changes on anything with a valid physobj

Parented props with broken inertia now display as [Unknown].
Fixed default inertia value when a prop is made spherical and has already had an inertia change apply to it.

Inertia now shows as changed if edited with E2/StarfallEx/other tools.
Can now copy inertia from props that haven't had their inertia changed before.

Rewrote the majority of the important code to fix a few major bugs involving inertia changing when duplicating stuff

Fix props not retaining inertia if made spherical with edited mass after being duplicated

Possibly fixed harmless lua error when nearly finished loading into a game

Fixed props without any inertia changes behaving as if they did. The bug in question is with inertia-changed entities being flung away if hit while frozen. This was happening with props that have never had their inertia changed.

- Added preset menu - Added inertia lock mode to keep inertia the same regardless of if mass changes - Fixed inertia changing unexpectedly after setting inertia, increasing weight without inertia lock, and duping then re-spawning - HUD now displays multiplier instead of actual inertia value when set to Multiple

Decreased minimum inertia