salted hash passwords

- new passwords (either for new users or people updating the password) are now stored with salted hashing (128 bytes salt / sha256)
- existing passwords are migrated when user signIn (only moment where the password is known clear by the server)
- maybe we should look for key stretching (bcrypt or pbkdf2)
use password_* for storing salted passwords

they are only available in php 5.5, but we use a userland compatible implementation in the meantime
correctly delete cookie in forums
prevent error for json lists when no result
do not call mobileVersion() more than necessary
replace php RSS parsing code by js/jquery

The goal is ultimately to get rid of calls to sfWebBrowser(), as this
blocks php when the remote resource is slow/unavailable.

No fancy layout yet, just a working prototype.
use an IIFE to avoid polluting global namespace
indentation consistency
use $.get().done()
meta rss: restore fancy layout
meta rss: display message by default, replace by content if there is some
Merge branch 'salted-passwords'
Merge branch 'prod'
inline JS metaengine rss parser
meta rss: nicer waiting/error messages
Merge branch 'get-rid-of-sfFeedPeer'
Merge branch 'master' of https://github.com/c2corg/camptocamp.org
invalid html
correctly retrieve banner size
Call-time pass-by-reference

useless + not allowed in php 5.4