Sync deleted appointments in shared calendars

* oc-folder: Flags are now used in indexing db when deleting a msg
* oc-folder: Make deleted items synched when shared
    * By keeping mid on moving messages by soft deleting and only if srcMid is different from targetMid.
    * Do not add soft-deleted messages in ensureIDsForChildKeys
    * Return soft-deleted messages on getDeletedFMIDs
    * Do not register a new mid if the URL is matched with soft deleted messages
* oc-folder: Uniform call to deleteMessageWithMID 

This also applies to Tasks/Contacts.
sorry, what I meant was:
<pre>
if (ret == MAPISTORE_SUCCESS)
    return idNbr;
return NSNotFound;
</pre>

or even better
<pre>
if (ret != MAPISTORE_SUCCESS)
  return NSNotFound;

return idNbr;
</pre>
later one has the advantage that if anyone is to implement additional idNbr manipulatin in future, she cat strart just from `return idNbr` - anything is handled already.