Support the ability to download project zip file #373

* A new button is displayed on the project page to download the project zip file
* One can use curl to download the project zip file
curl -O -J -k --get --data "session.id=<session id>&project=<project nane>&download=true" http://<websever host>:<port>/manager
If `inStream.close()` throws an IOException, the `outStream` may not get closed. You might consider using Apache Commons IO's [IOUtils.closeQuietly](http://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/IOUtils.html#closeQuietly%28java.io.Closeable...%29)