Added mine system saving

Don't forget to add this lines to mainConfig.sqf:

A3W_spawnBeaconSaving = 1;         // Save spawn beacons between server restarts (0 = no, 1 = yes)
A3W_mineSaving = 1;         	   // Save mines between server restarts (0 = no, 1 = yes)

Signed-off-by: Ivan <ivan_90.90@mail.ru>