Some description fixes

There are many more packages to fix, this is just a start.

Rules:
 * Don't repeat the package name (not always that easy...)
 * Start with capital letter
 * Don't end with full stop
 * Don't start with "The ..." or "A ..."

I've also added descriptions to some packages and rewritten others.

pkgs/development/libraries/apache-activemq/default.nix

@@ -22,9 +22,7 @@ stdenv.mkDerivation rec {
 
   meta = {
     homepage = http://activemq.apache.org/;
-    description = ''
-      Messaging and Integration Patterns server written in Java.
-    '';
+    description = "Messaging and Integration Patterns server written in Java";
     license = stdenv.lib.licenses.asl20;
   };