banip: replace the CARTO basemap with local outlines

banip: replace the CARTO basemap with local outlines

CARTO now requires an API key for the raster basemaps at basemaps.cartocdn.com and watermarks every unauthenticated tile request, so the GeoIP map currently renders "API KEY REQUIRED" across the whole viewport.
Therefore in luci-app-banip the basemap is now drawn from country outlines that ship with the package: Natural Earth 1:110m, public domain, all attributes stripped, simplified to 36 kB (~10 kB in the apk).

readme changes in the base package only

Signed-off-by: Dirk Brenken <redacted>