[IMP] mass_mailing: choose model among all chatter models

This commit removes the strange selection box based on a magic flag and
some strange methods returning a string. Instead just allow to send mass
mailing on all models inheriting from mail.thread using the is mail
thread flag.

Various addons are updated to remove the _mail_mass_mailing class
attribute used to determine mass mailing capability.

We consider people could send a mass mailing on every model inheriting
from mail.thread. It makes no sense to limit it to a given set of addons.

0 files changed, 0 insertions, 0 deletions