s/trigger/buskill_trigger in Config

This commit replaces the Config item name "buskill" with "buskill_trigger"

Apparently I silently renamed this option in the Config file some months ago when I was switching the Settings screen to use RecycleView, for the font accessibility feature

 * #55 (comment)

I don't know exactly why I made the change, but apparently I already updated it in other places, except here. The result: a bug where the first time you "arm" BusKill, it always defaulted to the 'lock-screen' trigger, instead of the setting the user already set it to.

 * #77 (comment)

src/packages/buskill/__init__.py

@@ -944,8 +944,8 @@ def toggle(self):
 			# set the default trigger to what's defined in the config file
 			self.config = configparser.ConfigParser()
 			self.config.read( self.CONF_FILE )
-			if self.config.has_option('buskill', 'trigger'):
-				trigger = self.config.get('buskill', 'trigger')
+			if self.config.has_option('buskill', 'buskill_trigger'):
+				trigger = self.config.get('buskill', 'buskill_trigger')
 			else:
 				trigger = 'lock-screen'
 			self.set_trigger( trigger )