* Namespaces protect symbols, I didn't consider that when adding
the BCodecKit namespace, so, the AddOnManager complained that
instantiate_plugin() was missing. A macro is introduced that allow
plugins to specify it's className, version and name, this ease
the declaration of the plugin symbols, otherwise the function
should have been declared inside the BCodecKit namespace which
we would like to avoid.
* The code is also more future proof, since in future the AddOn manager
can begin to check for plugin versions.
