Remember user preference to show/hide device type images in rack views

[hoalex]

Environment

• Python version: 3.6.8
• NetBox version: 2.9.3

Proposed Functionality

It would be nice if the value of the "Show images" setting on a rack view could be persisted as a user preference (using the mechanism introduced in #3294).

Use Case

We are making use of device type front/rear images on most of our devices in Netbox. By default, Netbox will render these images in a rack view, except when the user toggles the "Show images" button.
However, this is only valid for the current view -- as soon as another rack view is opened, or the current page is refreshed, Netbox falls back to the default mode, i.e. showing images.

Some users may not see any use in the images, and prefer to always see the name and device type color instead. Having a dedicated user preference key for this setting would allow for this functionality.

Database Changes

none

External Dependencies

none

[jeremystretch]

Reminder for whoever takes this on: Be sure to record the chosen preference name in docs/development/user-preferences.md.

[stale]

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[ogorov]

I could try to solve this issue.