WIP: Add setting for switching mapstyles

[ENT8R]

This PR fixes #673 and adds finally the functionality to show different mapstyles!
Currently the app needs to be restarted to change the mapstyle but I think this way should change as it is bad UX... I tested many things trying to achieve this functionality but it just didn't want to work 😕 Perhaps you can help me or give me a hint... 😄

What needs to be done:

• switch the mapstyle directly after the setting has been done
• change the api key of the satellite style (current key does not work and maybe you want to have control over it)

I'm also not that sure about whether it is right that I the streetcomplete.yaml file is now imported into every single mapstyle but I didn't find another way...

[ENT8R]

And of course it will fix #198 and #56

[westnordost]

Two comments on this:

I do not consider the dark style mature/ready as long as the rendering problems of the add blend mode exists (and that style uses that blend mode). If tangram-es guys do not fix this, perhaps a different less fancy blend mode could be used

I'm also not that sure about whether it is right that I the streetcomplete.yaml file is now imported into every single mapstyle but I didn't find another way...

SceneUpdates should make this possible. I.e. look at how I did it with the quest icons.

[ENT8R]

Ok. Then I will close this for now. I can come back later to this if all issues are fixed.

[ENT8R]

I do not consider the dark style mature/ready as long as the rendering problems of the add blend mode exists

Are you still facing these issues @westnordost?
Because I did some more work on this branch and I can't reproduce any rendering problems with either a device running Android KitKat or Android Oreo...
If you can't also see any issues, I would open a new PR 🎉

[westnordost]

I don't remember.

[ENT8R]

Alright... Then I will just make a new PR so you are able to test it too.