Fix grid

* The cube object is sliced in time and space before any download to improve performance (See `slice_bbox_extract()`;
* Fix circular grids;
* Make sure `get_nearest_water()` it finds all points;
* `get_nearest_water()` raises `ValueError` when data is not in the search radius;
* `get_nearest_water()` returns `None` if the point is located at dry land;
* Dropped `inline_map()`;
* Several clean-ups for clarity.