5.x - Update version-numbering pattern
## Tasks
* [x] `civicrm.org` - Update extension validation to accept 4.7 as synonym for 5.x
* [x] `civicrm.org` - Update extension validation to allow forward compatibility within 5.x series
* [x] *Upgrader* and `set-version` - Allow one to easily increment middle digit
* [ ] [doc](https://lab.civicrm.org/development-team/Release-Management/tree/master/doc) - Update RM docs
* [x] `5.x-rc.md`
* [x] `5.x-final.md`
* [x] `5.x-patch.md`
* [x] `test.civicrm.org` - Assess/update CI:
* [x] `civi-test-run`
* [x] `civibuild upgrade-test`
* [x] https://test.civicrm.org/job/CiviCRM-Core-Matrix/
* [x] https://test.civicrm.org/job/CiviCRM-Ext-Matrix/
* [x] https://test.civicrm.org/job/CiviCRM-WebTest-Matrix/
* [x] https://test.civicrm.org/job/CiviCRM-Core-PR/
* [x] https://test.civicrm.org/job/CiviCRM-Backdrop-PR/
* [x] https://test.civicrm.org/job/CiviCRM-Drupal-PR/
* [x] https://test.civicrm.org/job/CiviCRM-Packages-PR/
* [x] https://test.civicrm.org/job/CiviCRM-Publish/
* [x] https://test.civicrm.org/job/CiviCRM-Publish-Watch-Core/
* [x] http://download.civicrm.org/latest - Display multiple autobuilds/pre-releases simultaneously
* [x] `civicrm-core` - Trial run, using installer/upgrader/distmaker/test-suite on v5.0
* [x] `civicrm-core` - Update various copyright headers from "4.7" to "5.x".
* [ ] `civicrm-drupal` - SPECME: The *.info files are set to 4.7 and twiddled on release. For git-based deployments, should we do anything to maintain these?
* [ ] `civicrm-wordpress` - SPECME: The `civicrm.php` file is set to 4.7 and twiddled on release. For git-based deployments, should we do anything to maintain these?
* [ ] *Extension author outreach* - Grep universe for READMEs/docs. Send mail-blast with suggested updates.
* [ ] `civicrm-core` - The file `js/crm.angular.js` has a function with a "remove me" notice
* [x] `docs-publisher` - https://lab.civicrm.org/documentation/docs-publisher/merge_requests/87
* [x] `civicrm-sysadmin-guide` - https://github.com/civicrm/civicrm-sysadmin-guide/pull/75
## FAQ
__Q: Would it be better to say `v4.8.0` vs `v5.0.0` vs `v5.1803.0` vs `v18.3.0` vs `v33.0.0`?__
They're all basically the same. All of these options will give *someone* the heebeegeebees -- because we've been doing 4.7.x for two years, and anything that looks different will look different, and different is scary.
The fundamental message should be this:
* The change in number is superficial.
* The substantive editorial/QA regime for `v5.{$Y}.0` is (initially) the same as the previous `v4.7.{$Z}`.
* The new numbering makes it to easier to administer minor patch updates, enabling us to consider more fine-tuned maintenance regimes.
There are bikesheddy reasons to favor one or another.
__Q: But I think there should be substantive change!__
Grand! Please head over to #2 to weigh-in on proposals or add new ones! (Or, if you want to focus-in on the [main review criteria](https://docs.civicrm.org/dev/en/latest/standards/review/), feel free to open a pull-request in [civicrm-dev-docs](https://github.com/civicrm/civicrm-dev-docs).)
__Q: Does this mean you're going to start making more, bigger, scarier changes more often?__
No. This is strictly a superficial realignment of the numbers. In fact, the general tenor of editorial policy has been toward tightening rather than loosening standards.
issue