Error sending communication in the prefered communication language

[davidbeig]

When sending a communication using the admin module, it sends it based on the language defined by the user in the user table instead of the one in user_preferences.

We should be using the user_preferences table for this communications, and the user defined language as backup when it's not defined.

Also, it seems that some i18n texts are not being translated in the communication language but in the current language of the user creating the communication.