Dreamplug WiFi AP setup

1. Add hostapd and iw as depends.
2. Use initscript to create uap0 interface on boot. (On non-Dreamplug devices it will just exit.) Fixes #44.
3. Configure uap0 interface during first-run, if it's available.
4. Enable dnsmasq's dhcp server on 192.168.2.0 network.
5. Set HOME for etckeeper in first-run initscript. Fixes #40.