Pending work on graceful app upgrades.

Revert "Merge pull request #8439 from joshsusser/fixes"

This reverts commit ce8ac393, reversing
changes made to b0e7b6f6.

Revert "Merge pull request #8431 from joshsusser/schemadump"

This reverts commit 036d3e1c, reversing
changes made to 0c692f4d.

Revert "Merge branch 'joshsusser-master' into merge"

This reverts commit 0c692f4d, reversing
changes made to 2e299fca.

Conflicts:
	activerecord/CHANGELOG.md
	activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
	activerecord/test/cases/schema_dumper_test.rb