move memorial icon to SVG

[nebulon42]

Implements part of #1165.
Icon: nebulon42/osmic/memorial-16.svg

before

after

[matthijsmelissen]

Tester recognizes neither before nor after.

I'm not sure if this should rendered significantly/on low zoomlevels at all. Some mrmorials are significant landmarks, but others are very minor compared to yhe surroundings.

[pnorman]

I think the new icon is an improvement - but the basic idea of the icon needs revisiting, as in my experience it's not clear what it means.

[HolgerJeromin]

yes, the icon is good, but especially the german "Stolpersteine" are much too prominent.

[nebulon42]

Prominence: Agreed, but the icon is now smaller although sharper. This needs adressing by categorising using other tags.

Other icon: I thought about this a bit and it is hard to come up with something distinctive for memorial. The idea of depiciting a plate or stone with text on it is not so bad. Sometimes this are statues, but depiciting e.g. a head would not include all the other possibilities of memorial. The other icon I meant to use for monument (monument-16.svg) might imply a larger structure.

[althio]

Regarding the icon itself: 👍

Regarding previous comments: I very much agree with @math1985 and @nebulon42

I'm not sure if this should rendered significantly/on low zoomlevels at all. Some mrmorials are significant landmarks, but others are very minor compared to yhe surroundings.
Prominence: [...] This needs adressing by categorising using other tags.

As many other features, it would be great to have subtags and established rules (tiers for zoom threshold and rendering) so that:

• first tier: important/landmark/monumental features are rendered early (z16?) and maybe special rendering when second tier appears (slightly larger icon size? icon in square/circle?)
• second tier: common features are rendered at closer zoom levels (z18?)
• negligible features are not rendered or only a maximal zoom level and maybe special rendering (lighter as in private POI?).

[polarbearing]

@althio - would be good, but apparently (see #1066) subtags are not yet supported.
If the monumental features are tagged as monument they could get a different icon as proposed in #758.

[kocio-pl]

Sooner or later we will need the subtags rendering - memorial table and memorial cemetery are very different beasts.

[matthijsmelissen]

Memorial rendering clearly has issues, but at least everyone agrees that the new icon is an improvement, so I don't mind merging this.