Add on_load for plugins

This asynchronous function is called on all plugins right before the IRC
connection is made.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

omnibot/bot.py

@@ -45,6 +45,8 @@ class Bot:
             self.server_config.port,
             self.server_config.use_ssl,
         )
+        log.info("Initializing plugins")
+        await asyncio.gather(*[plugin.on_load() for plugin in self.plugins])
         self.connection = IrcProtocol([server], self.server_config.nick, loop=loop)
         # Register events
         # self.connection.register("*", self.on_message)