In order to enable/disable the button by js we need to set it enabled/disabled by js
Add on the delete page for calendar the same safety as in the delete page for meetings

This means: if javascript is enabled the delete button will be disabled until the checkbox
to confirm the deletion has been checked.
Fix deleting the meetings when deleting a calendar and fix information message

The meetings associated with a calendar have to be deleted for a calendar to be safely
deleted.

The information message should only be shown if the deletion went through.
Merge pull request #80 from fedora-infra/fix_delete

Fix delete