Bugfix and balance walls / siege

[elexis]

Walls are one of the greatest remaining imbalances in alpha 19 due to multiple bugs and imbalances:

Before the attack:

• Walls can be built very fast r17312
• The number of wall turrets is not limited by area ("min-distance"),

During the attack:

• Walls are instantanously repaired and without any resource costs #3707
• Pathfinder of the attacker yielding unexpected paths in mazes of obstructions
• Wall turrets having more range than every other unit
• Attackers fail at dealing enough damage
  • Regular champs are not (and shouldn't be) useful in attacking walls
  • Elephants die too quickly
  • Ranged siege doesn't deal enough damage and is destroyed by wall-turrets

After the attack:

• Walls don't decay in disconnected territory #3340

---

#3707 and #3340 should be fixed individually. The other issues (besides pathfinding) can be addressed in this ticket. Not everything must be fixed for a20, but it should become more reasonable.

[elexis]

Two alpha 19 replays of games that took extremely long due to the pattern described above.