The old bash-based parsing code was way too complex. Replace it with Lua.

As the default package list is now handled using the 'packages' directive,
explicit wpad-mini removals in target definitions can be dropped.

build-tested with 2016.1.4, boots but packet loss on eth0
omitted ata due to build errors

No sysupgrade support yet.

As the Gluon kernel won't be compatible with the OpenWrt upstream anymore,
we don't need the vermagic hack anymore.

This also takes us past the OpenWrt 15.05 final release.