Switch plant_nursery pattern to SVG [WIP]

[kocio-pl]

Related to #2045.

Warsaw, z17
Before

After

[imagico]

Here the sample clearly shows an error.

The SVG contains a stroke-width:0.125 which does not belong there - this however is likely not the cause of the error.

My guess is that Mapnik kind of auto-offsets/auto-centers SVGs (which is insane for pattern images) - since the forest pattern symbols cross the edges on all sides there is no offset but with the other patterns there are.

[kocio-pl]

I hope we can fix it somehow, but until then I would drop this PR.

[imagico]

From my point of view there are two ways to deal with that other than fixing Mapnik:

• adjust the symbol offsets of the pattern so that the symbols cross all edges like in case of the forest pattern - this is always possible.
• add an invisible geometry to the SVG that prevents Mapnik from messing with it.

[kocio-pl]

I don't know how to do it, but if you do, that would be great.

[imagico]

I re-opened imagico/jsdotpattern#3 because of this.

[pnorman]

add an invisible geometry to the SVG that prevents Mapnik from messing with it.

That's what we've been doing in the past.

[kocio-pl]

As this code shows some problems and it looks like there's nothing new for a month to fix it, I'm closing this PR now.

[kocio-pl]

It looks like new script fixes the problem here too. It's just 128 px (we don't have to worry about 512 px limit), so I can create new PR soon.