Add special rendering for shop=musical_instrument

[kocio-pl]

We should start rendering shop=musical_instrument, probably with this icon from osmfr-cartocss fork:

https://github.com/cquest/osmfr-cartocss/blob/master/symbols/musical_instrument.svg

[It was proposed in meta-issue #1402]

[nebulon42]

This icon is already in use for amenity=nightclub.

[kocio-pl]

I think it could be more specific - like guitar or piano. But wasn't it disco ball that we were trying to apply here or was it some other tag?

[kocio-pl]

My proposition:
1)

[lest69]

I know what it's supposed to be, but I'm concerned it could be confused with other things (shoe, ice skate, cleats, etc.). Can you maybe try a guitar?

[kocio-pl]

That was what I started with, but the result was rather poor, so I'm still trying:
2)
3)

[kocio-pl]

Another take:
4)
5)

[kocio-pl]

Hm, maybe saxophone would do...

@nebulon42 Do you have any ideas or actual drafts for this shop type?

[matkoniecz]

3. is the best from proposed ones

[nebulon42]

I have no special ideas. I think any musical instrument could work. 2 or 3 maybe, with some tweaking.

[daganzdaanda]

A trumpet is a good symbol, I think. Number 3) has no piston valves in the middle, maybe they could be added to reduce the "hole".

[kocio-pl]

So the popular opinion is clear - I will try to work with the trumpet.

[kocio-pl]

All about details, which are visible mostly at higher resolutions, and slightly better with current icon size:
7)

[matkoniecz]

I think that 3) is still the best (7 started to look like scheme of electronics, with diode on the left and resistor on the bottom).

[kocio-pl]

Maybe I have tried too hard to make everything visible (piston valves left untouched):
8)
9)

[matkoniecz]

to keep also 3) easy to compare:

3. 
4. 
5. 

[matkoniecz]

3. and 9) are the best.

[kocio-pl]

What about piston valves?