Change the "receive PM from" to "members allowed to contact me"

First of all: this is unfinished.

This PR addresses: http://www.elkarte.net/index.php?topic=76.0

The missing part is that I don't know where to put the setting...
At the moment is still in the PM config area, but is not the right place, "notifications" looks not good too, it should have its own page, but that would be overkill, other meaningful place in the profile it can be put?