Upgrade to Facets 2.x

[ekes]

I'm marginally confused that facets is needed here; but it certainly will be needed.

Upgrade is Facets dropping 8.x support and PHP 7.1 support. No schema alterations.

See also:

• https://github.com/localgovdrupal/localgov_news/pull/52
• https://github.com/localgovdrupal/localgov_openreferral/pull/23
• https://github.com/localgovdrupal/localgov_directories/pull/176

[ekes]

Dependencies now work : https://github.com/localgovdrupal/localgov/pull/409