Add field configuration for :include_in_request. If true, the field will...

... be explicitly added to the request made to solr. Otherwise, Blacklight assumes the appropriate configuration is made in the solr config. Attempts were made to keep this change backwards compatible with existing practice.

The configuration looks like:

```
config.add_facet_field 'yes_facet', include_in_request: true # will be added as a `facet.field`
config.add_facet_field 'no_facet', include_in_request: false # will not be added as a `facet.field`
config.add_facet_field 'some_facet'

config. add_facet_fields_to_solr_request! # add all facet fields to solr
config. add_facet_fields_to_solr_request! 'some_facet' # add the 'some_facet' field to the solr request
```

Same goes for `add_index_field`/`add_show_field` and `add_field_configuration_to_solr_request`.