Reference 4.1.1 in debugging rails applications guide from #15304
Escape user input before showing in the page.

This is not a security issue since this page is not present in
production and user have to type something in the field but is better to
escape the input.
Refactoring .reflections public method.

Now the internal reflections will hold a reference to its public
representation, so when the outside world calls `Account.reflection` we
can build a list of public reflections.

Conflicts:
	activerecord/lib/active_record/associations.rb
	activerecord/lib/active_record/counter_cache.rb
	activerecord/lib/active_record/reflection.rb
Merge pull request #15301 from zzak/issue_15212

Skip if the association was already loaded.
Add test case for b13d260
Move test to the proper file

All preload tests are in the eager_test file