Update Fedora Atomic page for F28 release
* Update curr_atomic_id and next_atomic_id
* Update Atomic iso name and link with new format
* Update checksum links for Atomic artifacts
to follow new directory structure, Now, both
Atomic iso and Atomic cloud images are produced
under AtomicHost directory.
* Use curr_atomic_id instead of cur_id on atomic page
* Replace reference of Docker with Container on
atomic page
Signed-off-by: Sinny Kumari <sinny@redhat.com>