Disabling insertMode

[newmangreen]

Hi,
Although I set insertMode: false at options, it switches back to true when I press INSERT key.
INSERT key is assigned for other function in our form, so we need to disable that switch.

This is mentioned here #2565 and it was commented before.
It seems a new option needed or better it should not change its behaviour if I gave it at options.

[RobinHerbots]

@newmangreen ,

Can you give an example of the mask and options you use. I tried with a random mask, and cannot reproduce the problem.