Refactoring louloulibs and cmake

Use OBJECT libraries
Remove the louloulibs directory
Write FOUND variables in the cache

Respond to MAM requests on a channel JID

At the moment, result-set-management is not implemented, the whole history
(well, at most 1024 messages) is returned.

Replace all include guards by #pragma once

It’s $CURRENT_YEAR

Style fix

Move all constructors at the top of classes

JID class provides bare() and full() methods

louloulibs is directly included, instead of being a submodule

Because this is a nightmare to manage