* Initial test and benchmark for mapEntity.Step().
* Removed `&& !m.hasPath()` from mapEntity.atTarget
* Direction is now updated when the path node changes mid-step and target is updated when path is set.
* Test improvements.
* Deleted old benchmark function and tidying.
* d2math.Abs added.
* Abs benchmark and optimisation.
* Negate and Distance benchmark.
* Length and SetLength benchmark.
* Lerp and Dot benchmark.
* Cross and Normalize benchmark.
* Angle and SignedAngle benchmark.
* Trivial change to Vector.Abs()
* Fixed NaN on normalize 0 vector.
* Tentative implementation in getStepLength.
* mapEntity.TileX/Y removed.
* Fixed Position and Target not being initialised in createMapEntity.
* mapEntity.Position is no longer embedded.
* mapEntity.LocationX/Y no longer used outside map_entity.go.
* mapEntity.subCellX/Y removed.
* mapEntity.LocationX/Y removed.
* mapEntity.OffsetX/Y and TargetX/Y removed.
* Direction method added to Vector, returns 0-64 direction.
* Moved Vector.Direction() to Position.DirectionTo and refactored.
* Renamed RenderOffset from SubCell and tested IsZero.
* d2math.WrapInt added for use with directions.
* Tidied up position and tests.
* Refactored d2common.AdjustWithRemainder into d2mapEntity.
* Tidying up d2mapEntity.
* Final cleanup.
* Lint warnings.
* Spelling correction.
* Comments and newlines in engine.go
* Comments and newlines in object.go
* Comments and newlines in animated_entity.go
* Comments and newlines in missile.go
* Comments and newlines in npc.go
* Comments and newlines in player.go
* Removed object.go (incorrectly merged it in during rebase).
* Comments and newlines in renderer.go.
* Comments and newlines in map_entity.go.
* Comments and newlines in walk_mesh.go.
* Comments and newlines in viewport.go and tile_cache.go.
* Comments and newlines in stamp.go and wilderness_tile_types.go.
* Comments and newlines in everything else.
* Add PushEffect, handle effects in renderer
* Set effects instead of blend
* Stop using PushCompositeMode, use PushEffect
* Remove remaining composite mode things
