Update clhs cost layer from raster package

[gcperk]

Update the current method from gdistance to raster. Initially leastcostpath package was suggested, however this also relies on raster objects and is slow.

Code to be re-written in Terra package compatible.

[kdaust]

The dev version of leastcostpath (from github) now uses terra instead of raster and is much faster! I'll work toward getting it done in that.

[gcperk]

Ok great - I was looking at the cran version. I am working up a version with the github V.2.0 release. It seems much faster, just trying to work out how to incorporate the road speeds...

some relevant examples / notes here:

https://gis.stackexchange.com/questions/280197/working-out-travel-time-from-gdistances-conductance-values-in-r
https://mran.microsoft.com/snapshot/2014-11-17/web/packages/gdistance/vignettes/gdistance.pdf
https://gis.stackexchange.com/questions/280593/understanding-the-values-from-transition-layers-produced-by-the-r-package-gdist

[gcperk]

Updated to new package least cost path, after testing this seems too generatizes and if not picking up the detail of the topography. Required digging into the calculations as to how the smoothing is generated (within the leastcost path package).

New version (see lower left corner for generalised costs)

Previous version using gdistance package (this is not 100% correct but notice the detail is much higher and closely related to topography).