Backport #5808

df36c5f - Fix assert_template assertion with :layout option
4bd05a7 - Fix assert_template :layout => nil assertion
0d19a08 - Improve assert_template layout checking
Merge pull request #9899 from macksmind/backport_5808

Backport #5808
Don't reset inheritance_column when setting explicitly.

This is backported from master (cdfcbc4).
Added changelog for 55e2954
Merge pull request #9576 from fredwu/backport_fix_explicitly_inheraitance_column_to_3_2_stable

[Backport to 3-2-stable] Don't reset inheritance_column when setting explicitly.
Fixed test failures on 1.8.7 caused by 74e59ea
Merge pull request #9943 from fredwu/test_fix_for_74e59ea

Fixed test failures on 1.8.7 caused by 74e59ea
Removing explain support warning from the Railtie

This is causing a regression since the Active Record Railtie is trying to
connect to the development database in the application boot.

See https://github.com/rails/rails/pull/6197#issuecomment-15199273
Add attr_accessible to the Getting Started Guide.

This was brought up in #9995, but is only present in 3-2-stable, since
mass assignment is removed from Rails 4.