FEATURE: navigate to first post and auto bump category settings

### navigate_to_first_post_after_read setting for categories

When enabled on categories logged on users will return to OP after
reading the entire category. (useful for documentation categories)

### num_auto_bump_daily

Set a number of topics that will automatically bump daily on a category.

- Every 15 minutes we will check if any category has this setting
- Categories with the setting are shuffled
- We exclude pinned, closed, category description and archived topics
- Maximum of 1 topic for the list of categories is bumped till limit reached per category
- We always try to bump oldest first
- Limit is elastic using a RateLimiter that ensures that we only bump N per day

Also some minor organisation on category settings

Froze strings on category.rb

app/controllers/categories_controller.rb

@@ -283,6 +283,7 @@ class CategoriesController < ApplicationController
                       :subcategory_list_style,
                       :default_top_period,
                       :minimum_required_tags,
+                      :navigate_to_first_post_after_read,
                       custom_fields: [params[:custom_fields].try(:keys)],
                       permissions: [*p.try(:keys)],
                       allowed_tags: [],