rg_calc_save: Adds together two raster layers, saves the result under path...
In sitscholl/Rgadgets: Contains various utility functions developed during the PhD

This takes two raster_layers x and y and a character vector as filename, calculates a new raster_layer by adding raster x and raster y and then saves it to path and returns that path

1	rg_calc_save(x, y, path, format = "GTiff", operation = "+", ...)

`x`	Raster layer
`y`	Raster layer
`path`	A character vector, the calculated Raster_layer will be stored under this path.
`operation`	A character vector, one of +, -, * or / specifying how x and y should be combined
`...`	Further parameters passed on to raster::writeRaster