donation of spells

provide room in castles for spells to be donated - perhaps make the spells take as much room as a dragon or a high level troop since its value (time and elixir) are similar. Give a cool down time on taking spells that are longer than troops so that a user who is requesting has to pay to use the feature frequently (like requesting troops too soon after expenditure)

This could be used to speed up spell production for a close clan war. Clan's that work together will have a better chance of helping their top level players go "over the top".