Add proper custom images system

[Fenrirthviti]

Currently, there is a placeholder for account profile pictures (they can be manually added by editing the DB). This needs to be updated to be:

• [x] Upload/update avatar picture. Potential this can be added to #4 next to name in chat
• [ ] Upload channel images
  • [ ] Static preivew
  • [x] Offline image
• [ ] Toggle in settings for live preview or static channel image

[Fenrirthviti]

Proof of concept of this has been complete, just need to implement into the settings page.

[Fenrirthviti]

Avatar upload has been implemented.

[Fenrirthviti]

Offline image display complete via https://github.com/Fenrirthviti/stream-site/commit/22b3b5a58ee7ee45577dee87465867799d9b5c2a

Pending static preview image implementation.

[highattack30]

Good Job