Remove unnecessary require from active_support/inflector/methods.rb

`active_support/inflections` already requires
`active_support/inflector/inflections`. There's no need to require it in
`active_support/inflector/methods`.
change to destructive `deep_symbolize_keys` after https://github.com/rails/rails/commit/df24b8790f22384a068fece7042f04ffd2fcb33e which allows to do so. This helps to avoid extra hash object creation, by symbolizing inplace
make "rails dbconsole" work with activerecord-postgis-adapter
Add test for AR::CounterCache.update_counters
Refactor AR's counter_cache_test.rb test
Use Range#cover? for Numeric ranges (tests via endpoints) and use Range#include? for non-numeric ranges

added changelog message
Remove OracleDatabaseTasks was deprecated, because this was provided by 3rd-party.
Remove SqlseverDatabaseTasks was deprecated, because this was provided by 3rd-party.
Remove FirebirdDatabaseTasks was deprecated, because this was provided by 3rd-party.
Change Result#each to return an Enumerator when called without a block.

As with #10992, this lets us call #with_index, etc on the results.
When .find_each is called without a block, return an Enumerator.

This lets us do things like call: .find_each.with_index
Fix undefined method `ref' for nil:NilClass for bad accept headers
Adding verbose mode to test_with_ar_integration
Adding verbose in isolated test.
We are now rails 4 [skip-ci]
removed unnecessary mapping for on options

Right before that in `assert_valid_transaction_action` method we make
sure that `options[:on]` contains values from `ACTIONS` array
(`[:create, :destroy, :update]`) and nothing more (i.e. it could not
contain strings or something else, otherwise the error is raised).

Also I've polished some docs.
Merge pull request #11095 from vipulnsward/rails_4_docs

We are now rails 4
Merge pull request #11096 from akalyaev/remove-unnecessary-mapping

removed unnecessary mapping for on options
change id="errorExplanation" to id="error_explanation" to match the generated files
Fix another "error_explanation" css class in guides [ci skip]