Improve Enemy Architecture

[umut-sahin]

• Adds an optional spawn interval for enemies within the group (e.g., 500ms after the level started, spawn 3 enemies with a 100ms interval)
• Searches for an empty space on the map to spawn the enemies intelligently and queues the enemies to be spawned later in a different place if an appropriate place could not be found.
• Implements debug in a smart way for enemy spawn patterns.
• Plus a few small improvements.