Add availability to configure show_image_direct_url

This commit:
  - Add the show_image_direct_url parameter (default to false)
  - Fix spelling errors in documentation
  - Fix documentation format (use puppetdoc)
  - Add missing documentation about params

(cherry picked from commit 715216c3dc313243ff566e380758cd495950988f)
Change-Id: I8e5cb36c19ffa4ae726642a55d8fab5c6cea07b5
Co-Authored-By: Emilien Macchi <emilien.macchi@enovance.com>
Havana: Fixtures: fix keystone branch name

Solve issue: « fatal: ambiguous argument 'stable/havana': unknown
revision or path not in the working tree. »

Change-Id: I10c7442fa8b322b5f78cdf7b8033205df95089ca
Merge "Add availability to configure show_image_direct_url" into stable/havana
Merge branch 'stable/havana' of https://github.com/stackforge/puppet-glance into havana