Add CRedit360 logo.
Merge pull request #254 from alastairs/add-credit360-sponsor

Add CRedit360 to the sponsors
put the correct date into the meta information
Merge pull request #258 from adrianbanks/fix-date-in-meta-tags

Put the correct date into the meta information
prevent the agenda being seen unless it should be

this also restricts access to the registration and accommodation page unless registration is open
Merge pull request #252 from adrianbanks/issues/251

Fix #251 Prevent the agenda being seen unless it should be