nbd: new package nbd-server

See http://patchwork.openwrt.org/patch/3409/
owfs: Add init scripts and config files

See http://patchwork.openwrt.org/patch/3416/
owfs: make libow features configurable

See http://patchwork.openwrt.org/patch/3417/
owfs: Bump version to 2.8p21

See http://patchwork.openwrt.org/patch/3418/