jhollist/elevatr: CRAN Release 0.4.2

elevatr 0.4.2 (2021-12-28) Additions

• OpenTopography now requires an API Key. This can be acquired form OpenTopography. You need to set it with elevatr using elevatr::set_opentopo_key(). After a restart, elevatr will use this key.
• The "Introduction to elevatr" vignette has been updated to include chanage reflected in version 0.4.2 and also includes a new section on accessing data from OpenTopography and details on setting the API key.

• The epqs server was occasionally returning an empty response (see https://github.com/jhollist/elevatr/issues/29) and would error. If that happens now, elevatr will retry up to 5 times (which usually fixes the issue). If still an empty response after 5 tries, NA is returned and a warning is issued indicating what happened.
• Changing to future::plans was losing tempfiles on parallel downloads. Moved the change back to serial plan after creation of raster.
• Changed get_tile_xy. My math was messing up in areas near 180/-180 longitude were trying to grab non-existent tiles. Now using slippymath::lonlat_to_tilenum instead.
• NA's introduced with simultaneous gdal mosaic and project. Now uses two steps. Solves https://stackoverflow.com/questions/67839878/gridded-dot-artifacts-in-geom-raster-plot