cmd_area_attack_tweak.lua: remove all but 1 CTRL+Area_Attack's attack queue when user append extra order with SHIFT

This it to make CTRL+Area_attack behaviour consistent with bomber_command behaviour.
cmd_area_attack_tweak.lua: undo adding "internal" tag to attack command (no need at the moment)
Merge pull request #17 from xponen/master

cmd_area_attack_tweak.lua: make CTRL+Area_attack consistent with bomber behaviour