Merge remote-tracking branch 'origin/wicket-6.x' into wicket-6.x
Models that depend on other models and behaviors for component
visibility/enabling based on models -- backported from the master
branch.
Replaced Java 7 functionality using Wicket util libraries.
Fixed broken tests.
Merge pull request #360 from ageery/wicket-6.x

Models that depend on other models and behaviors for component visibility/enabling based on models