Wicket 1.4.18 released

This is eightteenth release of the Wicket 1.4.x series. This is primarily a minor bugfix release on the 1.4.x (stable) branch.

<dependency>
    <groupId>org.apache.wicket</groupId>
    <artifactId>wicket</artifactId>
    <version>1.4.18</version>
</dependency>