fix initialize_as_grid and implement square_grid etc

[astrale-sharp]

add_square_grid(initial_offset: int, bounds: Rect2D , orthogonal_cost: float =1.0, diagonal_cost: float =INF, terrain: int=-1)
add_isometric_grid(initial_offset: int, bounds: Rect2D , orthogonal_cost: float =1.0, diagonal_cost: float =INF, terrain: int=-1)
add_hexagonal_grid(initial_offset: int, bounds: Rect2D , orthogonal_cost: float, terrain: int=-1)

[astrale-sharp]

I wont do it today but I might do it tomorrow!

[MatejSloboda]

I've already implemented them. Currently bounds can only be Rect2. I intend to add support for any arbitrary Shape2D, but it's more complicated than I originally thought.

[astrale-sharp]

nice!