Add alternatives to static-only for clearing the Dock

[TrevorBurnham]

• I made sure this command is not in the commands list
• I searched and didn't find this command in the listed issues
• I know this defaults command exists
• I know this command works on macOS current version
• I know this command is deprecated on macOS current version

• Folder: Dock
• Command: defaults write com.apple.dock persistent-apps -array and defaults write com.apple.dock persistent-others -array
• Argument type (if applicable): Array, but adding values is tricky. The commands above simply clear all existing items.
• Examples:
  • defaults write com.apple.dock persistent-apps -array opts all apps out of "Keep in Dock"
  • defaults write com.apple.dock persistent-others -array removes all folders and other items from the dock

Related to #62. cc @Darkomen78

Why?

Currently the site includes the static-only flag, which is described as Active applications only. I'd like to either removing static-only in favor of the commands above, or putting all of these commands on the same page.

Enabling static-only produces some counterintuitive behavior: You're still allowed to add items to the dock, but when you reboot, those items will disappear. Maybe some people want this, because it makes the Dock into a sort of temporary workspace, but I think most people would like to retain the ability to pin items to the Dock.

That's what the commands at the top of this ticket do: They clear items from the dock as a one-time operation, without changing the fundamental behavior of the Dock. That strikes me as likely to be useful to more people than static-only.