OPEN - #1: Upgrade to T5.4 
- the initial work for the upgrade is done but not properly tested
- esxx-httpclient-gae is now completely completely out. It's unclear
whether it's needed anymore (I don't see GAE users complaining about it
and at least at
http://krasserm.blogspot.com/2010/01/accessing-security-enabled-google-app.html,
the blogger seems to be using httpclient on GAE just fine). It has a
dependency to an old version of httpclient so either we'd need to
upgrade the library or remove it
- before any T5.4 compatible release, we need to at least rewrite the
JavaScript parts of the CollapsiblePanel component as a requirejs
module. The OauthSignIn.js can stay as a library because it's a
self-contained page