remove focus on cc_location

[mdsumner]

This was a natural function to write, because it gives a raster object for immediate use. But arguably, ceramic should be about the tiles and not create rasters - better would be

• create VRT lazy rasters from tiles in ceramic
• put cc_location() or equivalent in another package, with ceramic as one provider
• elevate get_loc() to a user-function, with a good name (it just gets tiles from a query, and tile source, type, format)

[mdsumner]

being heavily removed in https://github.com/hypertidy/ceramic/tree/get-tiles

get_tiles()