Required field mark (*) is displayed for read-only fields

In case if field is required, that red asterisk is displayed after field name to indicate that it's mandatory. This makes sense, when user can enter value in field, but doesn't make sense, when field is read-only, e.g. when "inp_label" block is used instead of "inp_edit_box" block.

I propose we add new parameter to all form blocks named "required", that could have 3 values:

• empty - automatic detection of asterisk presence;
• 1 - always display red asterisk no matter is field required or not
• 0 - always hide red asterisk no matter is field required or not