adopt Pecos performance fixes
remove the area filter, the performance fixes mean it isn't necessary
make more feature styles editable in property editor
let the NE layer trigger an update in the Overview when the resolution has changed, so that we show the correct set of child feature styles
handle more advanced editable styles
display some more advanced layesr
skip some more datasets
minor = remove comment line
index files
Refactor cached file so that it sits in the NaturalEarth plugin.