* plugin{.h,.c} are back but work in progress
* the interfaceregistry also manages a pluginregistry, makes no much sense
to isolate it yet, both share a mutex and are commonly used together
This ditches the old 'proof of concept' implementation, interfaces and
plugins are internally separate now and publically only accessed over
the 'interfaces' api.
The interface registry now gets an additional 'plugin' member to
backreference plugins from interfaces.
All interfaces which are available get registered in a tree.
This will be used internal for lookup interfaces. The higher level calls
will be an amalgamation of this lookup and the upcoming plugindb and
loader.
* lumiera_interface are now static structures, never wrritten
* introduced a lumiera_interfacenode which manages the dynamic data
of interfaces. The interfaceregistry now holds this nodes.
All interfaces which are available get registered in a tree.
This will be used internal for lookup interfaces. The higher level calls
will be an amalgamation of this lookup and the upcoming plugindb and
loader.
