Backend support for searching with tags

[lukavdplas]

The search view should accept a tags parameter, indicating that the query should be filtered on the given tags, which refer to a Tag

The backend should use this to construct and IDs query, which is a dict like the following:

{
	"ids": ["64738523", "84838923", ...]
}

This should be added as a filter ot the query JSON sent to elasticsearch.

[JeltevanBoheemen]

As per the documentation, should be:

{
    "ids" : {
        "values" : ["64738523", "84838923", ...]
    }
}