add meeting point option for units who can summon/spawn other units

[andy_5995]

I suggest adding an option that will allow units spawned by other units to go to a "meeting point"; the same way a meeting point can be selected from a barracks.

Example:
1. click on priest/summoner/shaman
2. click on a "meeting point" icon and select location
3. mummies/daemons/t-birds will move to the selected meeting point

[filux]

I've seen somewhere such thing in some techtree and it was very confusing (at least for me) because "the arrow" was visible during unit movements, so for example you choose to move it to the right but you see meeting point arrow to the top left direction .
Meeting point should be visible only then when unit currently doesn't move or attack, then maybe it will be an interesting feature.