MW 1.19 ExtensionMessagesFiles registration

Travis should have caught this because running unit tests locally against
MW 1.19 caused failures such as [1].

[1] There were 12 failures:

1) SMW\Test\DataValueFactoryTest::testNewTypeIdValue with data set #19 ('_num', 9001, '9,001', 'SMWN
umberValue')
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'9,001'
+'9&lt;smw_kiloseparator&gt;001'

Change-Id: Id52249c3cff763a494333cb133018bcc45aee92e