In meshes without VPN or supernodes, it may be desirable to connect a
router providing IPv4 addresses directly to a regular Gluon node. For
this to work, it was necessary to remove the gluon-ebtables-filter-ra-dhcp
package from the node, so the autoupdater also needed to be disabled.

To avoid this, make gluon-ebtables-filter-ra-dhcp disable the DHCPv4
filter rules when gw_mode is set to 'server'.

No solution is provided for RA/DHCPv6, but this seems less pressing for
local meshes, as nodes can already provide working IPv6 connectivity
by themselves through gluon-radvd.

This removes PKG_VERSION and PKG_RELEASE from most Makefiles, as the
value was never useful for Gluon packages; instead, PKG_VERSION is set
to 1 in gluon.mk.

It also removes two other weird definitions:

- gluon-iptables-clamp-mss-to-pmtu replicating the old PKG_VERSION logic
  from gluon-core, but without the fixed PKG_BUILD_DIR to prevent
  unnessary rebuilds
- gluon-hoodselector set GLUON_VERSION=3

These packages don't work or don't make sense without batman-adv.

the ports were interchanged, see the following packet flow:

client:546 --> [ff02::1:2]:547
server:547 --> client:546

therefore we need to allow outgoing multicast packets with dst-port 547
and unicast packets from bat0 to clients with dst-port 546 and 547 in the other direction