buttonMarkup: Add "role=button" to enhanced elements.
Unit tests: button-markup: Test for the presence of the "role=button" attribute.
Dialog: Add "role=button" to the close button.
Integration tests: Dialog: Make sure the attribute "role=button" is set on the dialog close button.
Custom select: Add "role=button" to multiple select popup close button.
Unit tests: Add test to make sure custom select is correctly enhanced.

Only the test for the presence of the "role=button" attribute for the custom multiple select popup close button so far.
Columntoggle table: Add "role=button" to the "Columns..." button.
Unit tests: Table: Check that the "role=button" attribute is set on the "Columns..." button.
Toolbar: Remove dependency on buttonMarkup and add "role=button" to "Back" button.
Integration tests: Add toolbar test.

For now, it merely makes sure a back button is added and that it has the "role=button" set.