Replaced stage spell arrays with structs containing AttackInfo fields,
which can be arranged in a human-friendly way. A pointer to such a
struct may be safely cast to an AttackInfo pointer, and treated as an
array for iteration purposes. Nothing should refer to spells via magical
array indices anymore.
Adapted all of the current spellcards into spellstages, which will
later be used in a spell practice mode a-la IN.
For now they are only accessible through the stage select menu or
by specifying their ID on the command line; both available only
if you built with -DTAISEI_DEBUG=1
