Add dependency on Dagger.

Add Dagger as an Ivy dependency, update the build file to bundle
the dagger runtime libraries with the client, and include Dagger's
license (Apache 2) so it's displayed in the UI.

Change-Id: Ie147032cd16a753868ad52b55f3406091cb672a6
Reviewed-on: http://gerrit.dmdirc.com/2643
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>