duplicate an AreaDefinition object with coarser/finer definition

Add a feature for the AreaDefinition class (https://pyresample.readthedocs.org/en/latest/geo_def.html#areadefinition). I would need a class method that creates a new AreaDef object from an existing one. The new AreaDef has the same projection and coordinate extent, but the grid_spacing (equivalently the number of gridpoints x_size and y_size) is scaled by a factor provided by the user. This would return a new AreaDef that matches exactly the existing one, but with twice (thrice, four times as much) the original resolution.

Example:

area_def = geometry.AreaDefinition(area_id, name, proj_id, proj_dict, x_size,y_size, area_extent)
new_area_def = area_def.finer_grid_spacing(3,2)

new_aera_def now has three times as much cells in the x axis, and twice in the y axis. If only 1 value is given, the same is used for x and y.