i18n Message improvements

During the Oslo meeting on 2013-10-11 (http://eavesdrop.openstack.org/meetings/oslo/2013/) we discussed the integration of Messages into OpenStack vs other approaches, and also came up with some ideas for improving the current implementation and on how to implement the translated logs feature.

After the corresponding blueprint is implemented in oslo (https://blueprints.launchpad.net/oslo/+spec/i18n-messages) we will have the ability to translate REST API responses, and to create additional logs in languages other than the default system locale.

This blueprint is for synchronizing the oslo code into cinder, re-enabling the lazy translation, and making necessary adjustments in existing messages so they are translatable (e.g. Messages should not be created with +, but with % instead).