Save the date of a claim

Hi,

Here is a small enhancement to the claim plugin, it now store and display the date when the claim was added.

I've also had to upgrade the parent to version 1.420 so that I could build this plugin with Java 7. I've fixed the tests following this update, I hope it does not have any side effect on the plugin behaviour (I haven't experienced any).

I've been used this patch since a few days and it's working fine.

Let me know if you could merge it as is or if it needs some improvements.

Reynald