Plugins check version

We should check plugin versions when loading them.  If the API changes
in a future version, then old plugins shouldn't work.

libsaria/plugin.py

@@ -81,6 +81,13 @@ def load_plugin_rest(name, file):
 		print "Error loading plugin: %s" % file
 		print e
 
+	try:
+		if mod.check_version() == False:
+			print "Error: plugin %s requires a different version" % name
+			return
+	except:
+		print "Warning: plugin %s doesn't check versions" % name
+
 	try:
 		globals()[name] = mod
 		loaded[name] = mod