Dynamic point icon symbology based on feature attributes

[raitisbe]

Feature Request

Is your feature request related to a problem? Please describe.
Only one image can be applied for features in a layer. To have different icons, we need to either create multiple rules or have multiple layers for each image.

Describe the solution you'd like
Icon url should be decided based on feature attribute values and {{ templates }} in a similar way how the label for TextSymbolizer is created.

Describe alternatives you've considered
Walkaround is to create multiple rules and filters with one IconSymbolizer per each rule-filter pair.

Additional context

[jansule]

Thanks for your contribution @raitisbe. I like the idea. So that's +1 from my side.

[jansule]

Done in #364