View config

Refactor `blacklight_config.document_index_view_types` into `blacklight_config.view`, so we can write view-type-specific configurations:

```
config.view.list.partials = [:show_header, :show]
config.view.gallery.html_title = :short_80_character_title
```

Also, add new configurations for title and icon if the default i18n and glyphicon aren't appropriate:

```ruby
config.view.gallery.icon_class = 'glyphicon-tr'
config.view.gallery.title = "Grid"
```