mailmanager: add address doesn't work

[erwin]

Adding a single address in the mailmanager (GWT admin interface) doesn't work.

adding a csv file does work and adding a single address from the form on the website also works.

So maybe that button can just be removed?

[erwin]

adding and deleting addresses from the list should also be checked for inconsistent states in de entity cache.

i.e. em.persist(mailUser); without mailList.getSuscribers().add(mailUser)

[erwin]

fixed in build 26