Option to disable update check

[Glandos]

Is your feature request related to a problem? Please describe.

My server doesn't have Internet access, so restarting filebrowser takes a long time, before it timeout.

Describe the solution you'd like

I check myself new releases via GitHub RSS feed, so I'd like to disable update check within filebrowser.

Describe alternatives you've considered

Additional context

[gtsteffaniak]

yeah, should be configurable. I'll add a shorter timeout too for update checks.

[gtsteffaniak]

added in 0.8.4