add first draft of web page for captive portal
make servald start and mount /serval before uhttpd starts
work on mounting filesystems on mesh extender in saner way,
and try fscking /serval-var.  Unfortunately fsck doesn't fit on
internal flash, so we can't fsck /serval easily.
also further tweaking (in vain) of cleanup-packages to clearout
enough of /overlay to allow reinstallation without running firstboot
from failsafe mode inbetween.