Changing borders color to gray [WIP]

[kocio-pl]

Related to #622.
Related to #3526.

Simple color change for the borders from violet to gray. Examples:

Warsaw, z12
Before

After

Europe, z4 (see more examples here)
Before

After (borders)

After (borders+water)

[HolgerJeromin]

Crowded city centers would be interesting

[Tomasz-W]

It looks very good on low- and mid-zooms, but I'd like to see some high-zoom examples, especially places where borders crosses or goes along other elements of map

[kocio-pl]

Could you give some examples to test?

[Tomasz-W]

A few places found fast, if you need, I can give more of it later
http://www.openstreetmap.org/#map=15/52.4786/16.7802
http://www.openstreetmap.org/#map=15/52.2668/16.9386
http://www.openstreetmap.org/#map=18/51.62556/14.75621
http://www.openstreetmap.org/#map=18/52.42021/16.92300
http://www.openstreetmap.org/#map=16/52.3220/16.6323

[kocio-pl]

The most convenient would be something included in Metro extracts.

[imagico]

The most serious problem at the low/mid zooms with grayish borders is interference with railways at z7 and above.

The German style using a somewhat greenish tone (much less green though than the old German style) is doing a bit better here but not really great:

https://mc.bbbike.org/mc/?lon=9.948721&lat=51.108173&zoom=7&num=2&mt0=mapnik-german&mt1=mapnik

At the high zooms you are also going to have interference with cliff:

https://mc.bbbike.org/mc/?lon=6.745563&lat=46.339865&zoom=13&num=2&mt0=mapnik-german&mt1=mapnik

cc @giggls.

[matthijsmelissen]

Note that this partially reverts #1749 / 5a0f036 .

[kocio-pl]

Thanks for raising these issues. Borders rework may include different pattern and changing levels like it's discussed in #622. I'd like to start with extending new midzoom landuse colors for low zoom to see how they will interact with borders. Green is unlikely (there will be more trees), but maybe gray+violet tint could work?

@nebulon42 wants to publish lowzoom tool which will save z8 landuses, so testing can take only reasonable time.

[kocio-pl]

There are many other changes related to midzoom going right now, so I close this PR. Borders needs probably more in-depth discussion anyway than this trivial color change.

[kocio-pl]

@imagico On the other hand we have other confusing things currently: #1248.