Fixes #5926 - hide sensitive parameter values

User can check to hide value when creating or editing global parameter.
The value is masked by *** and is also not displayed when overriding.

This is meant as short-term solution. Long-term we should move to smart variables and smart class parameters and add proper password support there. I know that similar patch would be handy for smart variables and smart class parameters, but it seems too much work which would be dropped later.