Revert core updates until Silkscreen can deliver its own #29
Description
Backdrop CMS introduced core updates in-place in 1.11. If this code were included in SilkscreenCMS, then the auto-update would "update" Silkscreen to Backdrop, which could break sites that use database configuration storage or any other non-standard driver.
Until the code and infrastructure necessary for Silkscreen to upgrade itself is in place, the auto-update code should be removed.