Crate actions can now define required prerequisites.
Update mods (only d2k and RA affected) crate actions to take tech levels and prerequisites into account.
Added YamlException to GiveUnitCrateAction if no units are defined.
Make ra light tanks be able to crush infantry to improve usefulness
and be consistent with the rest of the ra tanks and ra1's light tank
Fix legacy map importer. Fixes #6143.
Let ra apc and minelayers crush infantry too
disallow bots on poland raid
disallow bots on burlesca
Update CONTRIBUTING.md
Merge pull request #6212 from pchote/mapimport

Fix legacy map importer.
Merge pull request #6213 from ScottNZ/balance

Update crushing values for ra vehicles
Merge pull request #6189 from UberWaffe/6066_CratePrerequisites

6066 Crate Prerequisites
Merge pull request #6215 from Mailaender/poland-raid-bots

Disabled bots on maps with separate land masses between destructible bridges
Added `int subCell = -1` to IMove.MoveIntoWorld & IPositionable.SetPosition(Actor self, CPos cell)
Refactor MobileInfo.CanEnterCell
Fixed UnloadCargo stacking using new subcell API exposure
Refactored [sub-]cell availability logic in IPositionable & ActorMap

Moved the logic from IPositionable.CanEnterCell & integrated sub-cell selection.
Added IPositionable.IsMovingFrom(CPos location, int subCell = -1) - to detect transient actors
Renamed IPositionable.{GetDesiredSubcell => GetAvailableSubcell} - since it checks for available sub-cells
Reduced IPositionable.CanEnterCell to one method that usually uses IPositionable.GetAvailableSubcell
Added actor checking to ActorMap.{HasFreeSubCell, FreeSubCell, AnyUnitsAt} - used by [sub-]cell availability logic