Update Jetty to 7.6.8.v20121106

A user was having trouble with some of Jetty's NIO selector code. Not
sure yet whether this will fix the problem, but it can't hurt.

The newer version of Jetty also includes some manifest signature data
that is not compatible with Maven's shaded jar construction, so filter
those files out.

Change-Id: I043114e037f641b8277d0d7aa954b2e7af67876d

pom.xml

diff --git a/pom.xml b/pom.xml
index 3498a05..04efb57 100644
--- a/pom.xml
+++ b/pom.xml
@@ -33,7 +33,7 @@
   <properties>
     <!-- Should track Gerrit's jgitVersion fairly closely. -->
     <jgitVersion>2.1.0.201209190230-r</jgitVersion>
-    <jettyVersion>7.5.2.v20111006</jettyVersion>
+    <jettyVersion>7.6.8.v20121106</jettyVersion>
   </properties>
 
   <modules>