Rewrite the position-init code for carrier starts, to precisely wait
on the carrier model being loaded, before proceeding with FDM init.
This allows the FDM to see the correct carrier model in the ground
cache, and hence avoids starting in the water.
To implement this, the CheckSceneryVisitor is used to force the carrier
model to be loaded while the splash-screen is visible.
Wake computations are now performed for all AI aircrafts within a range lower or equal to the value indicated by the property /fdm/ai-wake/max-radius-nm.
These computations are triggered by the property /fdm/ai-wake/enabled (it is disabled by default).
The result of the wake computations is not yet used by the FDMs so do not expect the user aircraft to react to the AI wake.
This is too destructive for many established things, so revert it.
Instead, make the FDM shell save /fdm state on postinit(), and
restore it on re-init (which reposition invokes).
As part of this, kill off the evil global FDM state, and avoid us
copying FGInterfaces (which is bad since it contains TiedProperties
and an FGGroundCache, neither of which are especially keen on being
copied). Will probably disable copy/assignment on TiedProperties in
a future commit.
Untieing needs to be done prior to the destruction of the object which
aggregated the TiedPropertyList. So the TiedPropertyLists destructor can't
untie the properties automatically (and it doesn't). So, do some manual
clean-up.
Priority scheme for tile loading/removing
Cleaner tile manager interface for AI/groundcache/...
Reduce start-up delay. Drop splash screen when inner scenery is available.
Be nice to osg loader: slow-down main loop while initial scenery is still loading.
