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.
--HG--
branch : gsoc2011-guildmissions
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.
--HG--
branch : gsoc2011-guildmissions
