pending messages more accurately conveyed to user

Fix for #750.

During pending state, messages will be colored a faded:
* **blue** if the local user is registered for push and the destination address is either a push group or a single recipient in the push directory
* **green** otherwise

![pending](https://f.cloud.github.com/assets/373823/2276891/0ea3db78-9f39-11e3-8273-6d77da3edc09.png)
![notsent](https://f.cloud.github.com/assets/373823/2276892/1218e76c-9f39-11e3-8e7d-a4f955ed4880.png)