add ActiveRecord::AbstractAdapter#extensions and ActiveRecord::ConnectionAdapters::PostgreSQLAdapter#extensions to allow dumping of enabled extensions to schema.rb, add ActiveRecord::SchemaDumper#extensions to dump extensions to schema.rb

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

Having column related schema dumper code in the AbstractAdapter. The
code remains the same, but by placing it in the AbstractAdapter, we can
then overwrite it with Adapter specific methods that will help with
Adapter specific data types.

The goal of moving this code here is to create a new migration key for
PostgreSQL's array type. Since any datatype can be an array, the goal is
to have ':array => true' as a migration option, turning the datatype
into an array. I've implemented this in postgres_ext, the syntax is
shown here: https://github.com/dockyard/postgres_ext#arrays

Adds array migration support

Adds array_test.rb outlining the test cases for array data type
Adds pg_array_parser to Gemfile for testing
Adds pg_array_parser to postgresql_adapter (unused in this commit)

Adds schema dump support for arrays

Adds postgres array type casting support

Updates changelog, adds note for inet and cidr support, which I forgot to add before

Removing debugger, Adds pg_array_parser to JRuby platform

Removes pg_array_parser requirement, creates ArrayParser module used by
PostgreSQLAdapter

Fix GH #4259. We must remove table_name_prefix and table_name_suffix, when we execute schema dumper.

Fixes #3678

This reverts commit 3e4ede81.

Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

This will hopefully make Active Record run a bit more faster.

This will hopefully make Active Record run a bit more faster.