Add the ability to show all Pokemon at a specific zoom level

[RaizeTheLimit]

set '$showAllAtZoom' in config.php to the desired zoom level. All pokemon will be showed on the map when the user zooms to a level >= showAllAtZoom

Tested on my live map for a few weeks

[M4d40]

hmm, not all users might want to suddenly see all pokemon, would it be possible to add it to the frontend so users can change it themself?