Add 2 new actions for the mission compiler: recv_charge_point and
give_control.
Add the 'guild' option for some actions: check if the mission is
valid, and change the script generation to add this option.
mission compiler now checks if we are not asking several guild
members to complete an objective whereas the mission is not a
guild mission.
It also generates the 'nb_guild_members_needed' parameter for
objectives in the script.
