It's pointless to have libmm-common around, just merge it into libmm-glib and
make ModemManager depend on libmm-glib directly. At the end, the non-common
stuff in libmm-glib is really minimal.
Renamed `MMCommonBearerIpConfig' to `MMBearerIpConfig', and removed the
`MMBearerIpConfig' provided in libmm-glib. We'll just use the original one
from libmm-common always.