Lots of tweaks that make the what/which+noun questions all work

A variety of little things that make questions like this work:

"Which girl do you like?" "What book are you reading?"

NB: which+noun had been previously classified as a _quantity() relation; I changed that to a _det() relation, which makes more sense and is the standard grammatical classification -- they are question-word-determiners.

P.S. Also corrected a few ancient typos that I noticed, so I don't know if those might affect something someday . . .
And to make the rule only applied once (since there could be multiple verb with the flag), I think you can make the rule exclusive with itself.  
```
[IMPERATIVE] {1} <IMPERATIVE, DECLARATIVE> tense($verb, imperative) =>
```
In theory that should work, but I haven't tried that.