Add ranged combat support

* Clean up the CombatAction and Attack code to make it easier to use for
  range.

* Add collision detection to the distance checks before attacking in the
  CombatAction.

* Create a Ruby DSL for defining projectile types and fix the
  ProjectileUpdateOperation so it uses the correct position offset.

* Fix the packet structure of the HintIconMessageEncoder.

data/plugins/combat/ammo/arrows.rb

@@ -0,0 +1,15 @@
+def create_arrow(item, hash)
+  hash[:projectile_type] = :arrow
+  hash[:weapon_classes]  = [:longbow, :shortbow]
+
+  create_ammo item, hash
+end
+
+create_projectile_type :arrow, start_height: 41, end_height: 37, delay: 41, speed: 6, slope: 15, radius: 10
+
+create_arrow :bronze_arrow, level_requirement: 1, projectile: 10, graphic: 19, drop_rate: 0.3
+create_arrow :iron_arrow, level_requirement: 1, projectile: 9, graphic: 18, drop_rate: 0.35
+create_arrow :steel_arrow, level_requirement: 5, projectile: 11, graphic: 20, drop_rate: 0.4
+create_arrow :mithril_arrow, level_requirement: 20, projectile: 12, graphic: 21, drop_rate: 0.45
+create_arrow :adamant_arrow, level_requirement: 30, projectile: 13, graphic: 22, drop_rate: 0.5
+create_arrow :rune_arrow, level_requirement: 40, projectile: 15, graphic: 24, drop_rate: 0.6

data/plugins/combat/ammo/bolts.rb

@@ -0,0 +1,10 @@
+def create_bolt(item, hash)
+  hash[:projectile_type] = :bolt
+  hash[:weapon_classes]  = [:crossbow]
+  hash[:projectile]      = 27 unless hash.key? :projectile
+  create_ammo item, hash
+end
+
+create_projectile_type :bolt, start_height: 44, end_height: 44, delay: 41, speed: 5, slope: 5, radius: 10
+
+create_bolt :iron_bolts, level_requirement: 1, drop_rate: 0.35