Make the use of a backup configurable.

This adds the configuration option `use_backup` which can be used to turn off the loading of fixtures from a backup file if using SQLite.
Expose the created reference repository in the FixtureService.
2014 coding style update
Merge branch '2.5'

Conflicts:
	src/VIPSoft/DoctrineDataFixturesExtension/EventListener/HookListener.php
	src/VIPSoft/DoctrineDataFixturesExtension/Extension.php