Need a way to ignore some fields for "Leave page" warning

[nirgal]

Here's a feature request :

I'm having a few minor issues with confirmFormDiscard : While this is a nice feature, I occasionally would like to ignore some fields.
In my case, this is a "quick search" widget in the header for example.
But people have been reporting similar wishes like in filters (see #86).

I guess it wouldn't be too difficult to add a class/attribute/whatever to a form/field that would make the check ignore some forms/fields.

The idea would be modify formChange function, and check that an ignore-dirty / ignore-change / whatever is not present before setting the data-dirty attribute. Preferably in the whole DOM tree above the input element.