Store map size defaults in single location

[historic_bruno]

Since we have random maps now, there are several points where map sizes can be chosen from a list:

• In game setup, when playing a random map (gamesetup.js)
• In Atlas "New" dialog, when creating a blank map (/tools/atlas/lists.xml)
• In Atlas map panel, when generating a random map (/tools/atlas/scripts/section/map.js)

Instead of having 3 or more different lists that have to be sync'd, we could just store them in one location, maybe in a file with raw JSON data. This could be analogous to player defaults /simulation/data/player_defaults.json, where code that needs to access the data can go through the simulation. The file would be an array of map size objects, perhaps with tile size, name, and detailed description of each choice (for tooltips).

[ben]

(In [9608]) Adds player editor to Atlas scenario editor. See #91 Fixes object panel so the list of players updates correctly. Atlas map settings are now observable and shared between various panels. Fixes panels for maps missing settings (caused JSON error) Changes map reader so that entities with invalid players cause a warning but are not added to the game. That prevents further errors. Fixes #869 Uses map size choices from simulation/data/map_sizes.json instead of multiple locations. Fixes #787 Prepares Atlas map settings for undo/redo support