Enhancement: Search query term linking

We've added the option to search for multiple terms with the same type,
at the moment only the tag search benefits from it.

This makes it possible to search for multiple resources with different tags in one query.
The UI now empowers the user to perform advanced searches like:

* all resources with the tags `tag1` OR `tag2`
* all resources with the tags `tag1` OR `tag2` AND containing text `content`

as a rule of thumb, if a property appears multiple times (like `tag1` OR `tag2`)
the search combines the query with an `OR` and different keys are linked with an `AND`.

https://github.com/owncloud/web/pull/9854
https://github.com/owncloud/web/issues/9829
