Fix path to i18n

* This fixes the path to i18n the problem was introduced in the latest release.

* Renames msupload.php to MsUpload.php
* Renames msupload.i18n.php to MsUpload.i18n.php
* Renames msupload.body.php to MsUpload.body.php

Change-Id: I2ae068381e915f2b02378bef043ac767d27571f7