Refs #22601 - update DB gems from AR adapters

see rails commits 6a11d833ec and a9c06f61d5

Fixes #21084 - Always Use Rails 5.0, Drop Rails 4.2

fixes #19050 - add Ruby on Rails 5.0 support

Adds configurable support for running on Ruby on Rails 5.0 or 4.2,
defaulting now to 5.0 on Ruby 2.3 or higher. Ruby versions with partial
or no support remain using 4.2 by default. Other points:

1. SETTINGS[:rails] is loaded pre-Rails boot, then post-boot the...

fixes #15753 - unpin pg gem, match Rails requirement

Fixes #12219: Pin pg to 0.15.X

The pg gem from 0.16.0 to 0.18.4 breaks the ability to run database
rake commands due to an improper linking when ruby-devel is installed
and trying to use Ruby greater than or 2.2.2

refs #11719 - change pg/sqlite3 deps to match ActiveRecord

make bundler a bit more packaging friendly.