Find better way of detecting keyword rules

[lunakv]

The extractor determines whether a rule is defining a keyword / keyword action / ability word purely by the rule number (or rule section of that number). In the (admittedly fairly unlikely) event that either 701, 702, or 207.2c ever move, all of this breaks down. Therefore we should figure out a more robust way of detecting these rules.

The ability word list could be found based on some known text in the rule. This also isn't foolproof, but might be less likely to change if done properly. Once #27 is implemented, keywords and keyword actions can be found based on their ToC entries (I doubt they're going to rename the "Keywords" section).