Add GrantConditionOn*Layer traits
This allows to
- drop some booleans from Locomotor
- drop a good part of the subterranean- and jumpjet-specific code/hacks from Mobile
- grant more than 1 condition per layer type (via multiple traits)
- easily add more traits of this kind for other layers
Note: We might want to separate IsTraitDisabled checks later (possibly make the latter cancel the currently produced item), but that can be done in a follow-up.
