WL-1026 : A msg is public if it is public or its site is

Announcements made on a .anon site should be public by default.

Actually the code uses reverse logic : a msg is not public if it is not in a public site and it is not public

WL-1026 : doing a security check on channel

WL-1026 : Remove unused import

WL-1026 : Do security check in BaseMessage [message-util].

WL-1026 : Use reference for channel rather than depending on Site API.

WL-1026 : use m_userDirectoryService instance instead of static class
Merge branch 'WL-1026' of ssh://github.com/ox-it/wl-message into WL-1026

* 'WL-1026' of ssh://github.com/ox-it/wl-message:
  WL-1026 : use m_userDirectoryService instance instead of static class
  WL-1026 : Use reference for channel rather than depending on Site API.
  WL-1026 : Do security check in BaseMessage [message-util].
  WL-1026 : Remove unused import
  WL-1026 : doing a security check on channel
  WL-1026 : A msg is public if it is public or its site is