Added new MESSAGE_CONVERSATION_TYPE_SELF type for self-conversations
and upgraded legacy self-conversations to the new type, removing
repeated members in the message_conversation_members table.
Besides, from now, a self-conversation will be created by default for
all the existing users.
All the self-conversations have been also starred and a default message
will be displayed always to explain how to use them.
From 3.6 users can have also group conversations, so it's needed to review
the messages_get_messages function to make sure only returns the
individual messages between 2 users.
Also deprecated the following functions -
1. message_move_userfrom_unread2read - It is not necessary
for us to mark a message as read on user deletion.
2. message_get_blocked_users - Horrible logic used to
determine if a user is blocked via reference on some
randomly chosen 'isblocked' variable.
3. message_get_contacts - The same as above. This can be
done in a much nicer way.
4. message_mark_message_read - We want two functions to do
this to avoid confusing messages and notifications.
5. message_can_delete_message - This assumed the variable
$message contained the 'useridto' property, which
was present in the old table structure. We do not want
future usages where a query is done on the new table
and is simply passed as this won't contain this property.
6. message_delete_message - Same as above.
We are changing how the API behaves so the old tables will never
be populated. This unit test is testing a deprecated function
which we will not be refactoring to use the new table structure.
Also -
1) Made note of the deprecation as well as the functions and
files that were removed earlier in upgrade.txt.
2) Added new functions to api.php to replace the deprecated ones
that were being used in unit tests.
3) Removed files that are no longer being used.
