UnifiedMap VTM: Remove pseudo-3D display of buildings (or make it configurable)

[moving-bits]

Personally I find map display of buildings with UnifiedMap VTM confusing and harder to process than with old Mapsforge. I found out that there's a way to configure 2D/3D, so I propose to switch back to 2D (or make it configurable, if someone prefers 3D):

3D (currently)	2D (proposed)

(screenshots taken with OpenAndroMaps' Berlin map + Elevate theme)

[eddiemuc]

I strongly prefer the 3D look of buildings. Please don't remove it completely. Making it configurable would be fine for me though.

[MagpieFourtyTwo]

Don't like the 3D effect, too, cause buildings are way harder to recognize.

Which can perhaps be solved by drawing the roofs with a darker shading (already made some attempts to achieve this, but no success yet), but taking into account that there's no real information gain plus most probably higher CPU/GPU load for rendering, I would vote for 2D only, too, although an extra setting would of course be fine, too, but if so, I would suggest to set the default to false.

[eddiemuc]

Cruiser has such a setting:

[MagpieFourtyTwo]

Clever wording - cause "normal" is subject to evolutionary shifting. ;)

Nevertheless, just in case: I would prefer something more concrete like "3D buildings" or perhaps even "3D effects". :)

[devemux86]

3D buildings can be rendered normally or with shadows and extra OSM tags: roof, color, material, etc.

All these are included in the Mapsforge maps. 3D buildings are declared in the VTM themes.
Mapsforge themes do not declare them, so there is an extra rule in the code with default colors.

[eddiemuc]

Screenshot from c:geo VTM using a Mapsforge Offline map:

I like it!

[bekuno]

Screenshot from c:geo VTM using a Mapsforge Offline map: !
...
I like it!

Great!
We could integrate the configuration in the menu "Design options".

[moving-bits]

PR #15731 adds such an option to VTM offline maps' theme options.

Additional formatting for 3D mode (as shown in screenshot above) should go into a separate PR (and maybe differentiate between 2D / 3D (as today) / 3D (extended, as shown above).