Update user_manual/calendars.rst

Updated URLs to the correct ones for OC 4.0/4.5
New calendar images (created with 4.5.5)
Add link which is not fully shown in pic
Small adjustment to .com design
Merge pull request #25 from RandolfCarter/NewCalendarDoc45

Updates 4.5 calendar doc
Merge remote branch 'origin/stable45'

Conflicts:
	_shared_assets/themes/owncloud_com/layout.html