LRDOCS-317 Added explanation of the new Calendar portlet's calendar.sync.calevents.on.startup property for synchronizing data between the old and new calendar portlets

Conflicts:
	userGuide/en/chapters/08-collaboration-suite.markdown
LRDOCS-621 Added note that previously existing calendar events are added to each site's default calendar

Conflicts:
	userGuide/en/chapters/08-collaboration-suite.markdown
LRDOCS-621 Added a little more information about the calendar upgrade process

Conflicts:
	userGuide/en/chapters/08-collaboration-suite.markdown
LRDOCS-621 and LRDOCS-623

Conflicts:
	userGuide/en/chapters/08-collaboration-suite.markdown