[review] dcbw/ipv6-fixes: fix IPv6 support in core and plugins

[Dan Williams]

Please review and test!

Big changes in this branch (which we can change if we want to!) are that
by default, QMI, Ericsson/MBM, and Icera devices now read and send
static IP configuration in-addition-to/instead of DHCP, if we have those
details.  This is done for both IPv4 and IPv6.

For QMI, static configuration is always used, because we can always read
the IP addresses and DNS servers from the firmware.

For MBM, if the firmware supports E2IPCFG we use that information,
otherwise we fall back to DHCP/auto.

A main change in this branch is to modify the MMBearerIpConfig method
"DHCP" to pass some static information if we have it, instead of being
blank.  This could be an IPv6LL address and some IPv6 DNS servers, which
firmware often cannot or does not pass in DHCP or Router Advertisements,
due to awful IPv6 firmware support.  Connection managers should apply
this information, and still proceed with IPv6 SLAAC to get additional
information, like the public IPv6 address.  Connection managers may now
also get both IPv4 and IPv6 bearer IP config objects for the same
bearer, if "IPV4V6" contexts are used.

Dan