grid_couting_tax: Counting and rasterize multiple taxa occurrences
In gdauby/genmap: Mapping genetic differentiation for multiple taxa

Defining a grid of given resolution and counting occurrences for multiple taxa

1	grid_couting_tax(data, long, lat, sp, resolution = 10)

`data`	A dataframe with taxa field, longitude and latitude
`long`	A character string indicating the column name containing longitude in decimal degrees
`lat`	A character string indicating the column name containing latitude in decimal degrees
`sp`	A character string indicating the column name of taxa
`resolution`	A numeric indicating the resolution in kilometres of the grid