Implement a touch lock

[boa-pe]

It would be nice to have a lock function. This would prevent triggering unwanted actions by accidental display touch.

Just a button that needs to be long pressed to lock/unlock touch functions.

[wize-wiz]

Absolutely a must have.

[mfs12]

That would be good. I quite frequently hit the STOP button by mistake. Though perhaps when locked, STOP should still be accessible, for emergencies!

Eventually i makes sense to keep some few buttons on the lockscreen available.

• emergency stop

Although locked the screen should still display the the current page content.

Screen should be locked either with a button or timeout.

A password to unlock the screen needs to be configurable.

[mfs12]

The screenlock option should be on the Setup page i think

[mfs12]

Related to #169.