MAR-218: Switch to using fully-qualified collection names for all tasks:

- Ensures there is no ambiguity when invoking a module.

MAR-118: Replaced handler with parametrised name in wsgi_website:

- Updated wsgi_website role.
- Replaced handler with parametrised name used for restarting a single service
with a generic handler that will restart zero or more services.
- Updated test site roles to introduce explicit handler in them.
- Updated usage instructions to include set-up of explicit handler for
restarting the Wiki service.

MAR-114: Updated task syntax for web server/application roles:

- Updated web_server, php_website, and wsgi_website roles.
- Added and removed quoting where it makes sense.
- Switched to using expanded syntax (instead of one-liners).
- Updated ordering of arguments in task definitions.