add optional column parameter to isDirty
add optional column parameter to isDirty

This allows getting the dirty state of a single column.
Makes the api much more intuitive to use

kaufmo/koala-framework,kaufmo/koala-framework,Ben-Ho/koala-framework,Ben-Ho/koala-framework,nsams/koala-framework,koala-framework/koala-framework,nsams/koala-framework,kaufmo/koala-framework,yacon/koala-framework,koala-framework/koala-framework,nsams/koala-framework,yacon/koala-framework,Sogl/koala-framework,yacon/koala-framework,Sogl/koala-framework