We use the cache clear hook to index pages whenever the cache was
cleared.
This makes it possible to cover some cases like changing content on a
page. But also if an integrator configures to clear additional pages.
This is limited as we can not handle cache tags at the moment.
Resolves: #131
Do not limit integrator in possibilities to configure.
Therefore previously configure facets for a field need to be adjusted to
contain full configuration for elasticsearch. See changelog.
Resolves: #120