* Reorganize MapEngine
This is already turning into a mess...
* Map engine selects tile index to use
Still very ugly
* Fix subtile flag combination
* Prepare randomly generated base tiles
* Restore collision viewer
* Movement works again, searches for straight paths
Paths are now d2vector slices
* Fix LOS calculation
* Fix test (I think)
* Unnecessary constructor assignments removed.
* Position implemented in d2common.Path
* Position implemented in mapEntity.Step.
* Position implemented in d2common.PathTile.
* 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.
* Fixed nil pointer in Copy()
* Position added
Added Floor() and String() methods to Vector.
Also added Position which declares an embedded Vector2 and returns various forms of it.
* d2vector.Vector2 renamed to d2vector.BigFloat
* vector.go renamed to big_float.go
* Float64 stub and more renaming
* Vector value getters
* Separate vector types with initial methods.
* Divide and lint warnings.
* Distance and Length.
* Scale, Abs and Negate.
* CompareFloat64Fuzzy delta direction reversed.
* Refactor vector_test.go.
* Renamed Approx methods.
* Distance and Length.
* Distance and Length.
* Removed BigFloat and Vector, renamed Float64 to Vector, simplified tests.
* Angle, SignedAngle and other small functions.
* Receiver rename.
* SingedAngle and test fixed
* Rotate.
* SetLength.
* Cross.
* NinetyAnti and NinetyClock.
* Lerp and Clamp.
* Reflect and ReflectSurface.
* Cardinal convenience functions.
* Comments.
* Panic on NaN and Inf in Position.
* Lint warnings and comments.
* Fixed nil pointer in Copy()
* Position added
Added Floor() and String() methods to Vector.
Also added Position which declares an embedded Vector2 and returns various forms of it.
* Position tests improved
