Sample ofono binder plugin extension
====================================

It doesn't really do anything. It's just a demonstration of how
the extension interfaces (BINDER_EXT_TYPE_IMS being used as an
example) are supposed to be implemented.

Here is what happens when this extension gets loaded.

1. ofono calls sample_plugin_init(). That function creates an
   instance of SampleExt and registers it under the name "sample"
   by calling binder_ext_plugin_register()

2. ofono-binder-plugin finds the extension by name which it reads
   from /etc/ofono/binder.d/sample.conf

3. ofono-binder-plugin calls sample_ext_new_slot() method of SampleExt
   for each configured/detected slot. That creates per-slot SampleSlot
   objects.

4. ofono-binder-plugin asks SampleSlot for particular interfaces by
   calling its sample_slot_get_interface() method. SampleSlot only
   reacts to BINDER_EXT_TYPE_IMS query and returns a pointer to
   SampleIms object implementing BinderExtImsInterface

5. ofono-binder-plugin then goes on to call BinderExtImsInterface
   methods of SampleIms object(s).