"Number of questions" in quiz needs to be validated

Clarification: Number of qustions has to be both >= 1 AND <= the total number of available questions (meaning, those questions which are there *after* taxonomy filtering).

Ahem. :P

Clarification: Number of qustions has to be both >= 1 AND less-than-or-equal-to the total number of available questions, *after* taxonomy filtering.

The way taxonomy filtering is done, it's impossible to validate 'less-than-or-equal-to'. However:

1. Number of questions should be set to required
2. Should be validated to make sure it both exists and is >= 1.
3. Question selection screen should display a notice when selected questions are not >= the number of questions specified in the quiz options.

Bumping this so I can work on it tomorrow.

Finished.