all: Bump API and ABI version
server: Allow MediaServerPlugins to override search capabilities

Use a virtual MediaServerPlugin.search_caps property instead of hard
coding the value in ContentDirectory. This way plugin implementations
can represent their search capabilities correctly.

The default value is still the same: no change needed in plugins.

https://bugzilla.gnome.org/show_bug.cgi?id=712660
renderer: Fix GetCurrentConnectionInfo's p-i

We need to supply a proper protocol info in GetCurrentConnectionInfo if we
have one. This is even required by UPnP.

(Partially) fixes DLNA CTT 7.3.53.2

https://bugzilla.gnome.org/show_bug.cgi?id=706986