[FIX] ActivityHandler dispatched wrong activities to the host

Found this bug while playing around with awareness details.

Bug 1: Something is firing activities while only the host is in the
session after session startup

Bug 2: The ActivityHandler forwards those activities back to the host

Bug 3: The buggy RemoteEditorManager crap class registers the LOCAL user
with an active editor (which well never change again)

Bug 4: The bugged EditorManager along with its bugged classes is called
from bugged code which queries the RemoteEditorManager for open editor
states of the LOCAL user

Fixing bug 2 will prevent defects caused by 1, 3 and 4.

Change-Id: I183e5df84ce7c32659b93ced6a9a64a3808ed435
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1052
Tested-by: Jenkins CI
Reviewed-by: Patrick Schlott <pschlottk@gmail.com>
Reviewed-by: Franz Zieris <zieris@inf.fu-berlin.de>
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>