Pin Code tablet/emulator pages

[hadphild]

Can the Web Interface be Pin/Password coded?

http://127.0.0.1:8000/tablet.html

[josephdadams]

Relates to #573 , but we would probably want separate passwords for the tablet page, emulator, and main admin GUI.

[otelom]

Let's consider basic auth and also ability to disable emulators and tablet pages at all.
It's important to note that each browser's tab that loads this should require authentication, not like what happens now, because now we can only lock and unlock as a whole, the actual emulator for any browser that loads it.