Examples: restrict UI controls for scoreThreshold, minConfidence

[alexabruck]

I noticed that the examples were crashing when the user hit the plus button next to scoreThreshold or minConfidence settings, because at one point it will set them to 1. Both settings should be < 1.

I checked how this was solved on the official demo page of face-api.js: By setting the upper bound to 0.9. That's what I did here too.