Allow service item themes to change and be added back to slide controller

Break object link between saved item in slide controller and service manager.

Fixes: https://launchpad.net/bugs/806829

openlp/core/lib/serviceitem.py

@@ -352,6 +352,9 @@ class ServiceItem(object):
         Updates the _uuid with the value from the original one
         The _uuid is unique for a given service item but this allows one to
         replace an original version.
+
+        ``other``
+            The service item to be merged with
         """
         self._uuid = other._uuid
         self.notes = other.notes
@@ -461,3 +464,14 @@ class ServiceItem(object):
         else:
             return u'%s : %s' % (start, end)
 
+    def update_theme(self, theme):
+        """
+        updates the theme in the service item
+
+        ``theme``
+            The new theme to be replaced in the service item
+        """
+        self.theme = theme
+        self._new_item()
+        self.render()
+

openlp/core/ui/servicemanager.py

@@ -1348,7 +1348,7 @@ class ServiceManager(QtGui.QWidget):
         if not theme:
             theme = None
         item = self.findServiceItem()[0]
-        self.serviceItems[item][u'service_item'].theme = theme
+        self.serviceItems[item][u'service_item'].update_theme(theme)
         self.regenerateServiceItems()
 
     def _getParentItemData(self, item):

openlp/core/ui/slidecontroller.py

@@ -28,6 +28,7 @@
 import logging
 import os
 import time
+import copy
 
 from PyQt4 import QtCore, QtGui
 from PyQt4.phonon import Phonon
@@ -600,7 +601,8 @@ class SlideController(QtGui.QWidget):
         log.debug(u'processManagerItem live = %s' % self.isLive)
         self.onStopLoop()
         old_item = self.serviceItem
-        self.serviceItem = serviceItem
+        # take a copy not a link to the servicemeanager copy.
+        self.serviceItem = copy.copy(serviceItem)
         if old_item and self.isLive and old_item.is_capable(
             ItemCapabilities.ProvidesOwnDisplay):
             self._resetBlank()