Revert "Query guide: arel_table, eq and eq_any" along with other commits that added documentation involving the arel_table method

This reverts commit 578f9711.

Conflicts:

	railties/guides/source/active_record_querying.textile

Verify that there is no unwanted implicit readonly set on Model.has_many_through.find(id) [#5442 state:resolved]

Raise an error for associations which try to go :through a polymorphic association [#6212 state:resolved]

If a has_many goes :through a belongs_to, and the foreign key of the belongs_to changes, then the has_many should be considered stale.

Improved strategy for updating a belongs_to association when the foreign key changes. Rather than resetting each affected association when the foreign key changes, we should lazily check for 'staleness' (where fk does not match target id) when the association is accessed.

Revert "Optimize <association>_ids for hm:t with belongs_to source". The optimisation has too many edge cases, such as when the reflection, source reflection, or through reflection has conditions, orders, etc. [#6153 state:resolved]

This reverts commit 373b053d.

Conflicts:

	activerecord/lib/active_record/associations.rb

Test demonstrating problem with foo.association_ids where it's a has_many :through with :conditions, with a belongs_to as the source reflection

When a has_many association is not :uniq, appending the same record multiple times should append it to the @target multiple times [#5964 state:resolved]

Fix creation of has_many through records with custom primary_key option on belongs_to [#2990 state:resolved]

previously primary key value was always assigned nil which caused Oracle enhanced adapter failing tests

This is additional fix for commit
ebc47465 Respect the default_scope on a join model when reading a through association
which otherwise was failing on Oracle (as it returned fixture comments in different order).