Added importing spawn locations

[tcoliver]

I added the ability to import spawn locations directly from the 'spawn.json' file output by TBTerra/spawnScan. Users can utilize this to decide where to add new scanning locations and which locations can be omitted, rather than just covering an area completely. The spawn points show up as small red dots, which are fixed in place on the map.

My own use of this has allowed me to cover the same amount of area with my scans, while using only about half the number of workers.

[tcoliver]

Also, just in case you don't have a spawns.json file handy - here's a screenshot of the changes at work. the scan locations are manually placed over the spots with the most spawns, and it's easy to visualize where you dont need to scan at all.

[plebcity]

Very nice, I've been thinking about outputting every found pokemon to a database to get some more insight as to which pokemons spawn where and at which rate.