build: introduce luci-base Merges libs/core, libs/ipkg, libs/web, libs/sys, libs/sgi-cgi, libs/sgi-uhttpd, modules/admin-core, themes/base and protcols/core into modules/base and renames luci-lib-core to luci-base.
Add support for stateful DHCPv6
libs/core: mark radvd as affected by network restarts
libs/core: restart miniupnpd when firewall is reloaded
libs: merge libs/uci into libs/core