include: make firewall3 the default

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35888 3c298f89-4303-0410-b956-a3cf2f4a3e73
firewall3: add default config and firewall.user

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35889 3c298f89-4303-0410-b956-a3cf2f4a3e73