Performance improvements for Midgard1

In Midgard, we have some nice features, like dbus support, replication or quota. But not of them are mandatory by default. I ported some Midgard2 features, for better Midgard1 performance. Simply by making them optional and switchable on demand. All are enabled by default, for backward compatibility. But one can disable (or enable) any of them at any time.

API change is easy. To enable or disable:

midgard_connection::enable_dbus (bool);

For MgdSchema objects' CRUD methods: object is not serialized and no dbus message is sent.

midgard_connection::enable_replication (bool);

For MgdSchema objects' CRUD methods: 'repligard' table entry is not created or updated. Be aware. It affects getting object by guid only.

midgard_connection::enable_quota (bool);

For MgdSchema objects' CRUD methods: quota table is not queried or updated.

To check if feature is enabled:

bool midgard_connection::is_enabled_dbus ();
bool midgard_connection::is_enabled_replication ();
bool midgard_connection::is_enabled_quota ();