Feature/spawnattack at enemy

[titison]

1. Added the ability for SpawnAttacks to let the units spawn when the projectile arrives at the targetpos.
2. Added a bool spawnAtTarget to spawn attack in which you can define whether the unit spawns at the target or at the attacker.

In Addition i changed the command which is given to the spawned unit to an attack command on the target cell. Unit will always try to attack if it has an attack command.
( I think this makes way more sense than giving a move command to the meeting point)
( This also works if the spawned does not have a attack command. It will move to the enemy then)

so the "new" syntax is <unit value="warrior" amount="10" spawnAtTarget="true" />
if you want to let the unit spawn if the projectile arrives you need to use titi's new projectile syntax and add the unit node to it
Example:

            <projectiles>
                <projectile attack-start-time="0.25" damage-percentage="100">
                    <particle value="true" path="particle_proj.xml"/>
                    <hitsound enabled="false">
                        <sound-file path="$COMMONDATAPATH/sounds/archmage_hit.wav"/>
                    </hitsound>
                    <unit value="warrior" amount="10" spawnAtTarget="true" />
                </projectile>
            </projectiles>

Ask me if you have any questions