Passive voice detection

[mDuo13]

You can estimate the number of instances of passive voice by looking for instances of an auxiliary verb (am/are/were/being/is/was/be) followed by a word ending in "ed" or a pre-populated list of irregular past tense words. It's not foolproof, but it's enough to recognize when a sentence is overusing passive voice.

The Style Checker should report the proportion of sentences with passive voice detected in all pages. This can be an "information-only" detail by default. To make it involved in pass/fail, one would add goals for the proportion of detected passive voice instances per sentence. (Ideally the ratio is probably ~10%.) This would probably work similar to the readability scores in the style checker now.