Use script.module.libtorrent to import libtorrent

In order to support more systems (especially the ones where the
libtorrent python bindings cannot be installed manually), the add-on
script.module.libtorrent is now used to import libtorrent.

addon.xml

@@ -4,6 +4,7 @@
     <import addon="xbmc.python" version="2.25.0"/>
     <import addon="script.module.addon.signals" version="0.0.3"/>
     <import addon="script.module.requests" version="2.22.0"/>
+    <import addon="script.module.libtorrent" version="1.2.0"/>
   </requires>
   <extension point="xbmc.python.pluginsource" library="main.py">
     <provides>video</provides>

service.py

@@ -145,7 +145,7 @@ if __name__ == "__main__":
 
     # Import libtorrent here to manage when the library is not installed
     try:
-        import libtorrent
+        from python_libtorrent import libtorrent
         LIBTORRENT_IMPORTED = True
     except ImportError as exception:
         LIBTORRENT_IMPORTED = False