LUSpellSelection: some more fixes for proper window unloading in iwd2
iwd2::cg: let mages and sorcerers pick some initial spells
iwd2::cg: don't reset the Finish button to Accept at the last step
OpenSpellsWindow: skip if there's nothing to learn

eg. with bards that start casting only at later levels
CharOverview: make the Finish button default

now you can cruise through the whole iwd2 cg