Defaults for things like user agent and UAProfile should be modifiable
using a file installed by the hardware adaptation package.

Logging functionality that used to be part of mms-engine has been
migrated to libglibutil

MMS_CONNMAN_NEMO defined from the command line conflicted with the macro
defined in mms_connman_nemo.c

It can still be overwritten by MMS_ENGINE_VERSION macro, it's just that
now we have a reasonable default for it.

We need to use org.nemomobile.ofono.ModemManager API to notify ofono
that we need to download MMS so that it enables mobile data for the
appropriate SIM. If it's different from the currently selected data SIM,
then connman will be prevented from using mobile data while MMS download
is taking place.

These are mostly for convenience, the actual OBS build is using makefiles.

It didn't match the spec

Allows applications to determine which version of mms-engine is installed.

Previously, MMS settings were stored right in the IMSI directory at the
root of the dconf namespace. They have been moved to /imsi/ folder and
MMS settings now live in the mms subfolder, i.e. /IMSI/ -> /imsi/IMSI/mms/

Old settings are migrated to the new location the first time they are
requested. Instead of GSettings we now directly use DConf because it
appears to be impossible to properly implement migration with GSettings.
That makes gschema obsolete but we need to keep it around for backward
compatibility reasons.

The value is configurable from the command line and via GSettings

There are too many log modules to print them all every time when help
is requested. Fine-tuning per-module log levels is a fairly rare task.

This commit defines MMSSettings interface but doesn't actually implement
persistent settings. The implementation will follow as soon as it becomes
clear which kind of storage to use.

I suspect that some issues in the field might be related to the value
of the User-Agent header. Better have it configurable.