Added queue_name_delimiter attribute.

- Added ActiveJob::Base#queue_name_delimiter to allow for
  developers using ActiveJob to change the delimiter from the default
  ('_') to whatever else they may be using (e.g., '.', '-', ...).

- Updated source guide to include a blurb about the delimiter.
Allow Relation#rewhere to work with infinite range values
UrlGenerationError are not catched as 404 anymore
Fix rbx generated Gemfile regex

https://travis-ci.org/rails/rails/jobs/39190983#L460

 1) Failure:
 AppGeneratorTest#test_psych_gem
 [test/generators/app_generator_test.rb:495]:
 Expected /gem 'psych',\s+'~> 2.0', \s+platforms: :rbx/ to match <snip>
 http://git.io/uuLVag)\ngem 'psych', '~> 2.0', platforms: :rbx\n\n
Merge pull request #17405 from DanOlson/rewhere

Allow Relation#rewhere to work with infinite range values
Merge pull request #16229 from byroot/stop-swallowing-url-generation-errors

UrlGenerationError are not catched as 404 anymore
Optimize TimeWithZoneTest#strftime
Merge pull request #17310 from pabloh/optimize_strftime

Optimize TimeWithZoneTest#strftime
Merge pull request #17408 from bf4/fix_rbx_test

Fix rbx generated Gemfile regex
Fix doc markup for `NumberHelper` [ci skip]

The character "*" is unnecessary in option candidates.
This incorrect markup was injected in e8c9aeca .
Merge pull request #17416 from tricknotes/fix-doc-markup

Fix doc markup for `NumberHelper`
Deprecate the `only_path` option on `*_path` helpers.

In cases where this option is set to `true`, the option is redundant and can
be safely removed; otherwise, the corresponding `*_url` helper should be
used instead.

Fixes #17294.

See also #17363.

[Dan Olson, Godfrey Chan]
Mention only_path deprecation in release notes [ci skip]
Typos in the deprecation message
Merge pull request #17039 from zv1n/add_prefix_delimiter

Added ability to configure the queue_name_prefix delimiter to ActiveJob::QueueName.