Add TabFolder changes to migration guide
Add TabFolder changes to migration guide

The `TabFolder.textColor` property has been replaced with a set of
new properties which provide more control over the appearance
of the TabFolder.

Change-Id: Ieca43bca3de0ff17fb66f7bd03b36d33738ad333

eclipsesource/tabris-js,eclipsesource/tabris-js,eclipsesource/tabris-js