core: reworking client/server communication. Now uses ubf-encoded messages with client side delegates.
TODO: documentation and retry of timed out messages from server to client.
Issue #793
core: Refactored z_stats, now uses exometer
Add ack from client to server, retry messages if no ack received.
Add registration of sessions per user, for user level messages.
Add simple queue pruning on timeout.
Add 'dup' flag to messages that are re-send.
Issue #793.
core: fixes for ack messages.
Added support for pruning the session and page transport-message queues.
Issue #793
core: easier API for transporting messages to an user, session or page.
Might need ACL checks for user level messages.
Issue #793
core: ubf serialize the js proplists with binary keys, to prevent unknown atoms on the server.
Cleaned up and commented z_transport.
Issue #793
core: misc fixes and changes for transport.
Issue #793
docs: add documentation for the new transport mechanism.
Issue #793
docs: fix erlang texts in transport doc.
Issue #793
mod_admin: initialize z_editor when switching language tabs. fix #792

Signed-off-by: Marc Worrell <marc@worrell.nl>
core: increase maximum image size for previews

#796
mod_base: Export controller_logon:set_rememberme_cookie/2

It was inconsistent that it was not exported while the other 2
cookie-related functions were.
core: added notification #action_event_type to extend the wire types for action-event.
Issue #795
core: misc fixes to transport/pubzub.js.
Issue #793
mod_mqtt: add {% live %} tag for templates that update after messages are sent to mqtt topics.
Also add the {mqtt topic=...} event type for wiring actions and postbacks to mqtt topics.
Fixes #795
Issue #793
mod_mqtt: documentation for scomp live and the mqtt event type.
Closes #795
Merge remote-tracking branch 'origin/mw-transport'

Conflicts:
	src/support/z_session_manager.erl
docs: Fix edoc generation.
docs: add MQTT pubsub and transport to the page 'Interactivity: Calling Zotonic from Javascript'
docs: minor fix in live scomp