Extend documentation regarding disabling of installers

[UlrichThomasGabor]

Please extend the documentation regarding disabling of certain installers.

My first thought was that you have to list types, i.e. wordpress-plugin, which does not work. My next thought was that you have to list the filename of an Installer, i.e. WordPressInstaller, which also does not work.

Only after searching the code where this is actually implemented and going backwards from there I found the array keys which I can use. This seems a bit too much search work to me.

A table of the possible values would be really helpful at this point of the documentation; just like above with the available types.