[feature] Support down ranking of spells in Classic

[BreakBB]

This is related to #177 (maybe fixes it entirely).

It allows users to add specific spell IDs and Cell will respect the rank related to that spell.

The default list of spells is not changed, so users still have to enter the correct spell ID to actually use a lower rank.

[ekfuhrmann]

Any movement on this getting merged into stable?

Edit: Actually in testing this, I'd suggest that it uses highest level ability UNLESS you manually input a lower spell ID.

[BreakBB]

Thanks @ekfuhrmann I'll try to look into this and update the PR accordingly.