Math: Move convertcore to the local directory

There's no need to try importing a system-wide copy (for now) as convertcore
is our own munging of convertall's code into a form that's easy for us to use.
This may change in the future.

Signed-off-by: James Vega <jamessan@users.sourceforge.net>

plugins/Math/local/__init__.py

@@ -0,0 +1 @@
+# Stub so local is a module, used for third-party modules

plugins/Math/plugin.py

@@ -40,7 +40,7 @@ import supybot.utils as utils
 from supybot.commands import *
 import supybot.callbacks as callbacks
 
-convertcore = utils.python.universalImport('convertcore', 'our_convertcore')
+convertcore = utils.python.universalImport('local.convertcore')
 
 baseArg = ('int', 'base', lambda i: i <= 36)