search for nearby entities (objects or NPCs)

[diamantoula]

• [x] create new class
• [x] get user's current location
• [x] connect to database
• [x] fetch objects and NPCs from database
• [x] find if there is an entity close to the user (define radius)
• [x] create method for setting markers on the map
• [x] if there is an entity close by then set a marker of it on the map