This patch makes it easier to configure existing placement rules only with string.
1. placement(n) rule can be used to reuse earlier definitions
2 .&& can be used in addition to all(n1,n2)
3. country(c) accepts exclusions (like '!RU'), regions ('EU','EEA'), all and none
See the 'full example' unit test, which uses all of these, in a realistic example.
https://github.com/storj/storj/issues/6126
Change-Id: Ica76f016ebd002eb7ea8103d4258bacd6a6d77bf
* Handle failed country code conversion.
* Avoid potential issues with a data-race due to shared slice.
Updates #6028
Change-Id: If7beef2619abd084e1f4109de2d323f834a6090a