[3.0] Jumping to later installer steps is possible without a prior SMF installation having begun

[MisterVector]

In an environment with just a blank database, it is possible to go to a URL, such as: http://fork.development.local/smf/install.php?step=4

The installer will then start to install the forum without any prompts from previous steps.

[Sesquipedalian]

Yeah, we should end all use of URL parameters in the installer and upgrader, and instead rely entirely on the stored data that we write to Settings.php during the process.

[jdarwood007]

The url was a hold over from the old installer logic to help restart the upgrader should your browser stop. But since we write the upgrader data to Settings, we could drop this. But perhaps we could keep it in some form. Maybe just a hashtag set of data? It does help understand where along the process it should fail with an unexpected fatal error.