Bug 29072: Move reference route /cities spec to YAML

Bug 29072: Move reference route /cities spec to YAML

This patch moves the /cities routes spec and related files into YAML so
devs can use it as a reference for future routes.

To test:
1. Run:
   $ kshell
  k$ prove t/db_dependent/api/v1/cities.t
=> SUCCESS: Tests pass
2. Apply this patch
3. Repeat 1
=> SUCCESS: Tests still pass!
4. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>