WIP refactor getPokestopMarker to show both rocket + reward

[yw2theorycrafter]

getPokestopMarker has a lot of code duplication, in my opinion. This makes it hard to customize the appearance of pokestops. And, the existing implementation can't show both a rocket head + reward, and in this case it will only show the rocket head - which seems backwards, I'd prefer to see the quest reward!

This PR simplifies the whole thing to take a "merged" approach, where the html field of the marker icon is built up in stages. Rocket heads always go in the lower left, rewards on top of the marker.

TODO: This PR doesn't respect the "noRocket", etc. variables. I'm not sure it needs to, since aren't those things enforced in raw_data.php any way? Either way I didn't do it because I, personally, don't restrict them on my map.

TODO: I don't set the "class" correctly. If it has a rocket I set the rocket class, otherwise I just set the default marker class. I'm not convinced we're getting anything out of the custom CSS classes for the different marker categories, given that the thing you'd really want to customize is the size and placement of the rewards (which is hardcoded in getPokestopMarker...)

Some examples with this PR:

[kbtbc]

Something to further consider, is that until two days ago all Pokestops had two possible quest rewards, depending only if the player had an 'AR Mapping' quest in their inventory or not. Niantic just disabled the 'AR' set of quests, but I expect it will return, and eventually we should be able to display A/B quest rewards as well.

[jepke]

Would you be able to base this on staging/develop branch as those have a completely rewritten icon approach based on UICONS.

https://github.com/UIcons/UIcons

[yw2theorycrafter]

@jepke OK.

Closing in favor of #552.