Check read permission in getRepoFile * Inject PermissionBackend to all API entry points and pass it to hasReadAccess. * Add new ACL read tests in IncludeIT and OwnersValidatorIT; share code in FindOwners. * Improve readability in IncludeIT and ParserTest. Change-Id: Ia10601eb00980b62f08c240b91da81ee0c38d0df