Replaced documentation for config.action_controller.raise_on_unpermitted_parameters with documentation for config.action_controller.action_on_unpermitted_params.

I think that these signs are probably mistake.

to avoid unnecessary reg ex parsing and code
<http://httpd.apache.org/docs/2.2/mod/core.html#location
(recommended by @jja). - @erikj

[ci skip]

[ci skip]

This reverts commit dd319600.

This reverts commit 814c9875.

Adds documentation for:
- Aggregate cache keys,
- using an ActiveRecord model as cache key and
- Russian Doll Caching.