Dashboard cell: Add image cell

**Proposal:**
In Grafana it’s possible to have an "image" cell that displays decoded base64 strings stored in a database as an image.

**Current behavior:**
base64 encoded string is not decoded:
```
data:image/svg+xml;base64, PD94...
```

**Desired behavior:**
Image should be displayed.

**Alternatives considered:**
Use Grafana.

**Use case:**
Camera sensors to display traffic etc.