Combine scope conditions using AND

Currently Post.active.inactive will result in Post.inactive since
the last where clause wins when scopes are merged.

This pull request will merge all scopes ( barring defaul scope)
using AND.

The default scope will be overridden if another scope acts on the
same where clause.

closes #7365
If an index can't be found by column, use the index name.

schema_statements uses the column name by default to construct the index name, and then raises an exception if it doesn't exist, even if the name option is specified, which causes #8858.  this commit makes index_name_for_remove fall back to constructing the index name to remove based on the name option.
Unprepared Visitor + unprepared_statement
Merge pull request #9553 from neerajdotname/7365-mergin-scopes-and-where

7365 merging scopes for where clauses
Write a more comprehensive CHANGELOG message [ci skip]
Update test name to reflect change in how scopes merging works

Introduced in f1082b8588a9144eedb34d511f0074031f692d98.
Full changelog in 9f007d7fe5f90257c71baa2c4e7c76fb44512986.

[ci skip]
Merge pull request #9609 from arunagw/using-latest-arjdbc

Using latest AR-JDBC for JRuby
Merge pull request #8966 from cfabianski/disable_prepared_statement_when_preparing_a_query

Unprepared Visitor + unprepared_statement

Conflicts:
	activerecord/CHANGELOG.md
Merge pull request #8868 from tehgeekmeister/master

Use the index name explicitly provided in a migration when reverting.

Fixes #8868

Conflicts:
	activerecord/CHANGELOG.md
Fix rails console --sandbox

I've also added a proper acceptance test which reproduced the issue.

Closes #9513, #9515.