[repo] Add a publish/subscribe mechanism for inter-instance communication using zmq
Each repo can have a publishing and any number of subscribing sockets
whose addresses are specified in the instance's configuration. An
application or cube can subscribe to some 'topics', and give a callback
that gets called when a message matching that topic is received.
As a proof of concept, this introduces a hook to clean up the caches
associated with the repository when an entity is deleted.
A subscription is added using Repository::zmq::add_subscription;
the callback receives a list representing the received multi-part
message as argument (the first element of the message is its topic).
Once you have read the `RQL tutorial`_ and you know the application'`schema`_,
you're ready to define your own views. Just type the RQL query retreiving data
you're interested in in the search field. If the view used to display them
doesn't fit your need, choose another one in the possible views box (this box
isn't displayed by default, but you can activate it in your `user
preferences`_). Once you're satified, add a `bookmark`_ if you want to reuse
this view later.
.. _`RQL tutorial`: doc/tut_rql
.. _`schema`: schema
.. _`user preferences`: myprefs
.. _`bookmark`: doc/bookmarks
Below are some example of what can be acheived...
.. winclude:: custom_view_last_update
.. winclude:: custom_view_rss