User settings for auto updater

Add settings to the settings window for enabling and disabling automatic update checks.

Note that this is separate option to disabling the updater entirely, which can only be done from registry.

Start by locating the settings window and the automatic updater implementation. Trace how update checks are enabled and how the registry-only updater setting is handled. Done means the settings window can independently enable or disable automatic update checks without disabling the updater entirely.

Written by the indexing model from the issue text.