Find/replace `(?<=\w) {2,}` with ` `

Reading for content; editing for consistency.

Reading for content; editing for consistency.

Reading for content; editing for consistency.

Reading for content; editing for consistency.

Reading for content; editing for consistency.

Reading for content; editing for consistency.

Reading for content; editing for consistency.

Previously it read that you only needed to create a release on *subsequent* releases, but my experience was that the extension was not available until the initial release was made also. Rewrote to clarify this.

Also made a few additions to inline docs on the create a release node page. These can be recorded over in CiviCRM.org website repo via Features.

Refs #323.

ref:
https://github.com/civicrm/civicrm-dev-docs/pull/301#issuecomment-324795431

Originally there were different types of extensions - payment processors, reports & modules. For a long time only modules have been recommended and I feel documenting the others only adds confusion.

https://wiki.civicrm.org/confluence/display/CRMDOC/Example+of+creating+a+payment+processor+extension

https://wiki.civicrm.org/confluence/display/CRMDOC/Testing+Processor+Plugins

https://wiki.civicrm.org/confluence/display/CRMDOC/Create+a+Payment-Processor+Extension

https://wiki.civicrm.org/confluence/display/CRMDOC/What+is+a+Payment+Processor

https://wiki.civicrm.org/confluence/display/CRMDOC/Page+Templates

https://wiki.civicrm.org/confluence/display/CRMDOC/Customize+Built-in+Profile+Contribution+and+Event+Registration+Screens

mark `<requires>` and `<ext>` as experimental, and link to the PR which
makes them functional.

https://wiki.civicrm.org/confluence/display/CRMDOC/Add-on+Formats

- `<classloader>`
- `<psr4>`
- `<requires>`
- `<ext>`

I don't know what these do, so I just added them with "not yet
documented"