Dev issue164

[sdiaz7]

Features implemented (issue #164):

• Enemies apply damage to home when in contact with it. They no longer get destroyed by touching home, and will keep atacking until killed by towers.
• If an enemy gets blocked, it will target nearby towers and start attacking them. Attacking a tower is treated the same way as attacking home.
• Enemies look at their target while attacking.
• The script resets the enemy if it gets frozen (static for more than 2 seconds while not attacking).
• This branch does NOT implement animations, those will be integrated at #165 .

Recommendations for testing:

• Untag enemy prefabs to prevent them being killed by towers.
• Increase the time between enemy spawnings to prevent home from being overcrowded, or increase home's health.