Escape user id following XMPP protocol specifications

[vipod]

In these commits we applied bunch of fixes to escape user ids, so that, for example, even email addresses will work for user ids. Actually this was our use case: make jarn.xmpp.* bundle work in plone with 'email as login' feature switched on.

We escape user ids both on server and client side. Escaping procedure was implemented according to XMPP protocol specifications.

[ggozad]

Awesome! I am happy to merge as is, would it be possible update changelogs, readme etc, including instructions and migrations if necessary for existing installations? I think since the storage is affected it might be necessary to provide an upgradeStep, if not let me know and I will cut a new release.

[vipod]

Okay, we'll get back to you once all above things are reviewed. Another thing I have to mention is that we were not able to make collaborative editing work properly on our installations, so completely disabled it and using only 'messaging' functionality. That's why the changes made in this pull request haven't been tested with collaborative editing. So this is one more thing we should probably check now.

[ggozad]

Thank you! Do not worry about j.x.collaboration. There have been changes in tinymce that completely break it anyway, so it is not an issue with your code.