Simply documented and tested config to activate range limit facet

[jrochkind]

In the old days, you activated a range limit config with eg

config.add_facet_field 'pub_date_si', label: 'Publication Date Sort', range: true

At some time that was changed to use a default_range_config method mixed into CatalogController...

config.add_facet_field 'pub_date_si', label: 'Publication Date Sort', **default_range_config

The former simpler way of doing it now works again. And you can override other default config simply by adding the config you want to override:

config.add_facet_field 'pub_date_si', label: 'Publication Date Sort', range: true, range_config: { textual_facets: false }

Changed docs and tests to go back to simpler original way. Also will include specific docs for over-riding Components.

For now, the mixed-in default_range_config method is still available in CatalogControllers.. we could remove it, it would be backwards incompat with any existing config, but it is a major version, any thoughts? I'd just leave it in for now prob... maybe deprecate?

[jrochkind]

not sure why CI isn't running, but I built on top of #274 to avoid conflict, so will rebase and make Ready when that one is resolved.

[seanaery]

This looks like a good change to me, making this syntax what's recommended in the README. Nice to see that works again, as it feels cleaner/simpler. No strong opinion on whether to drop, keep, or deprecate support for **default_range_config.