Include our license list in the WAR file

Technically speaking, we should include the full copy of licenses
and associated notices within the binary distributions, even though
we point users to the project site and the documentation.  Copying
the current license table into the WAR file satisfies that.

Signed-off-by: Shawn O. Pearce <sop@google.com>

pom.xml

@@ -386,6 +386,9 @@ limitations under the License.
                   <fileset dir="${basedir}/target/executablewar" includes="**/*"/>
                 </copy>
 
+                <copy tofile="${d}/LICENSES.txt"
+                      file="${basedir}/Documentation/licenses.txt"
+                      overwrite="true"/>
                 <copy todir="${d}/WEB-INF/extra">
                   <fileset dir="${basedir}/src/main/java">
                     <include name="GerritServer.properties_example"/>